These are achievements you will gain for completing the tutorial and the main campaign.

Complete the Tutorial
Note that the tutorial is optional, not part of the main story so it must be selected.

Kill an enemy unit

Battle The Black Mountains: Kill Azuk

Complete the Campaign
This achievement is received for completing level 13, "The Origin,"

The numbered sections below relate to each of the 13 main campaign levels. Within each battle can be multiple achievement requirements, some not achievable on the same play through. For example "Doors are closed" requires a slower approach than "Strategist of The Flood", which must be completed as quickly as possible.

Win the battle The Black Mountains without losing any unit.

Win the battle The Forest in 13 turns or less.

Battle The Forest: Win the battle without getting any unit asleep
I need to look into this one a bit more. I got this trophy even though I did have units put to sleep. Maybe it's because I always woke them up straight away, or maybe it's a bug. Either way there are a couple of Goblin Mages who can cast SLEEP on your units. They will not cast sleep on any unit which is already next to another unit. Try to stay in at least pairs and keep out of their Move + Range and rush them with a group of ranged units to take them out before they can attack.

Win the battle The Flood in 12 turns or less.

Battle The Flood: Win the battle without opening doors
This doesn't mean what I first assumed. You have to avoid opening the door with your scout as instructed and must complete the entire level without your main party leaving the spawn area. The hardest bit is the first two enemies - remember that you are still in range of Cendor's Turn Back and the Priestess' healing ability until you move out of range.

After you warp past the wall and deal with the first catapult where you can cross the river, one of the orcs will show an interest. Bring both scout and you should be able to kill him before he can land a hit. Deal with the 2nd Catapult as normal. From this side of the river you can take out any orcs along the left bank who are mobile.

The third catapult needs care. You WILL get hit by the Armoured Orc protecting it. And it will take you 3 Scouts' worth of hits to take him out, so bring the other Scout through the wall at the same time if possible to start chipping away.

Near the switches, I haven't found a way of sprinting past the Armoured Orcs without losing a scout and failing, so best to deal with them. Make use of the fact that the Scouts' range is 4 and the Armoured Orcs only move 2. You can keep them at bay while you finish them off. Once they're gone you can hit the switches. The big Orcs will have appeared by now, so flooding the river should also get you the achievement "The Bridge on the River of Farabel", if you don't already have it and assuming one of your scouts doesn't die, you will also get "Strategist of The Bridge".

Win the battle The Prisoners without losing any unit.

Battle The Prisoners: Kill an opponent with an enemy catapult shot
Fairly straightforward. If you ensure that you are on the opposite side of a catapult circle from an enemy, they should more forward to melee you and get caught in the hit. Chip them down to 5 HP or less first, then end your turn.

Win the battle The Ancient Gods in 9 turns or less.

Battle The Ancient Gods: Kill the Boss destroying only one of the two pylons
The key with this, because the boss isn't going to go down quickly, is to protect weaker unit. The Ancient God can kill a healthy Scout in one turn. These turn into Lesser Gods and then you have more stuff to deal with. Make sure you count the spaces and keep the scouts 8 hexes away from the Ancient God. My advice is to teleport into range and then move back, because you can move further than you can teleport.

Save your Rage and Turn Backs mostly for the boss. Remember that on your melee fighters they will get hit for 12hp damage but you can only heal 8hp. So, combine the Turn Back with a good Rage hit to get 12hp healing AND deal the Rage damage twice. Also the Ancient God gets two counters, even at range, so hit him with two different units at full health, then continue with multiple attakcs and bringing the priestess in for healing. The priestess is a vulnerable unit here, because she'll take more damage than she can heal, but keep her out of range and the Ancient God should be tempted by closer targets.

When the Ancient God is on low HP, it will get a circular attack that does 5 unblockable, which it will follow up with a double strike on a weak unit. It can't really be avoided, so be sure to heal back up to full health and take out the new minion first. You aren't in a hurry with this achievement and letting a Lesser God roam around your units is going to create more issues.

I have a video of me doing what needs to be done for this achievement, however I ran into a bug and the boss didn't die at 0hp. But the approach is still there. The bug has since been fixed. https://youtu.be/Pju1mmClvzI

Win the battle The Goblin Sappers in 12 turns or less.

Battle The Goblin Sappers: Kill a total of 80 goblins in a battle
My score for this level is actually 122 and I used the following approach to unlock this. I fought back to the first spawn point and cleared the enemies and left a single Scout in firing range of the goblin spawns. Every turn when two new goblins spawned they could be killed by a single unit. I pushed down the map until I was able to repeat this on the second spawn point, however you need to prioritise killing the two Goblin mages, otherwise they will make your life hell with sleep status and a 6HP attack. Two mages can kill a Scout in a single turn. However two Scouts can take a out a mage with 2x5HP attacks each. Remember that their Teleport ability can pull them back out of range after firing.

Once the first two spawn points are camped, move the rest of your force to defend the "T-Junction". Wave after wave of goblins will rush forward. They don't do a great deal of damage, but keep the Priestess nearby to make sure everyone is healthy. Don't forget Cendor's lightning which can clear out loads of Goblins every other turn. If you have to choose, focus on killing the Goblin Snipers over the standard melee Goblins as snipers can hit your back rows and draw you forward. Hopefully you still have a spare Scout who can more forward, take out the snipers and then Teleport back.

Achievement should pop after a while. The Mounted Troll will appear after a certain number of turns, regardless of whether you have closed the portals. You might want to shut the first two portals down when he appears and bring your other Scout down the map to help. The Mounted Troll will prioritise hitting the Priestess with his laser beam attack (8HP) so make sure she can duck out of view to heal. However, when she is at full health, make her an inviting target to ensure that the Mounted Troll fires at her and then melees your soldiers, so avoid losing units.

This achievement will pop at 80 kills, so it doesn't matter if you fail the mission after getting it, unless you are going for record high score.

Win the battle The Walls without losing any unit.

Battle The Walls: Win the battle by preventing enemies enter the stairs
To get this achievement, you must complete the level while retaining a 0/5 score for enemies slipping by the stairs. Thankfully most enemies will engage you once you get close enough to be hit, so they can be diverted from their path, but to get this achievement, you need to keep your troops spread well and not bunched up too far to one side of the map. The enemies can cross the wall and be on the stairs in 3 turns, so try to keep a few skirmishes on the opposing side to your main fighting force to buy you time. Keep the pristess around the middle so that she can bolster stranded units if need be.

Battle The Walls: Kill a total of 40 enemies in a battle
I think (check needed) that 40 is the total number of enemies which spawn during "Battle the Walls", so if you successfully complete this, you will do it at the same time as "You Shall Not Pass!"

This level is a great place to unlock the achievement "Accurate Catapult"

Win the battle The Citadel without losing any unit.
Cunning use of the catapult should make this simple. Focus on getting enemy hit points low with the catapult so that once they are in range they can be killed in one hit by other units.

Battle The Citadel: Kill an enemy with the explosion of an explosive goblin
The explosive goblins are the ones with green gas raising off them. When they die, they explode damaging all surrounding units for 8HP unblockable damage (not reduced by armour). So avoid killing them with melee units (although the Farabel Guard will knock them back before they explode, if there is a space behind them) and do kill them with the catapult or archers. This achievement will pop if you kill one next to another enemy unit with 8HP or lower.

Win the battle The Gates of Farabel in 9 turns or less
The key to this is taking out the healers early. Maximise the catapult and destroy them. The mounted troll looks like a priority, due to it's 8HP laser beam, but realistically the combined massive force will cause you more problem. Clear up the little units first and try and rotate strong units to block the Mounted Troll's path to allow injured units to get clear for healing.

The key to this level is saving some Rage and - this is essential - at least one of Cendor's Turn Back abilities for the boss healer. The Boss can restore all 50 of its HP in a turn, which is more than you can inflict in one turn. Hammer it as hard as you can, then after it heals, use Cendor to Turn Back and negate its healing (if you don't already have it, this will unlock "It was better before"). Also, you want to do as much damage as possible, so don't push the Boss into a corner. Use the Militia to knock it out where it can be surrounded and you can rotate hitters. Additionally the knockback will protect the militia from the boss' powerful counter-attack.

Battle The Gates of Farabel: Kill Orak without the Turn Back Time ability of Cendor
I need to check the exact criteria for this. I have this achievement and can't recall what I did. I would imagine that you need to keep every unit alive and save their rage for Orak.

Win the battle The Catapult in 25 turns or less
Should be fairly straight-forward. Try to attack enemies in a way that allows you to keep moving forward and watch out for the two catapults hidden in shadows behind the trees. If you have to run past an enemy, don't worry. If they're interested they will catch you up and you can kill them. Completing this mission is down to hitting each of the marked Hexes and getting to the boat, not killing all enemies.

Battle The Catapult: Summon The Elemental in the first Turn and keep it alive until the end
Fairly self-explanatory, make sure to cast the elemental in turn one and keep it alive. This can be challenging because the elemental is a huge target for the enemy and they love piling into it. But it has pretty high HP and resistance, so make sure the Priestess isn't too far away and you should be able to keep the elemental topped up with more health than it can lose.

Win the battle The Bridge without losing any unit
This can be tricky. Until you have a unit on the bridge, the triple catapults will make your life very difficult. Keep your units out of the crosshairs, but don't let them get cornered. Sometimes they might have to take the 5HP hit, but don't stand in the centre because that deals 8 HP. But look out for where catapults overlap, as this will inflict double damage.

Sometimes a lucky catapult will destroy the boxes near the start of the bridge. You can anticipate this and head in more of a straight line one they are out of the way. The Cave Trolls will attempt to punch your units back into the catapult target area, so try to ensure they cannot get around you. However if you form a defensive line to the right of a catapult crosshair, most enemies will blunder into the area and get hit by the catapult. This gives you a lot of free damage and space to recover.

The Skull Throwers are responsible for a surprising amount of unit loss in this level, so I would recommend using the Ballista to take these out in one shot whenever they appear, although the Ballista can also be used to drop the mounted Goblins to 1 HP for an easy kill. These can be troublesome if you allow them a straight Charge. Additionally, you don't really want the Shaman to get to the main fighting area, so consider sniping them with the Ballista over two turns to prevent their arrival. Remember to move wounded units together with a space for the Priestess to join them, as she will give 1 HP to every wounded adjacent unit at the end of her move. This is a lot of free healing.

Battle The Bridge: Kill 4 enemies at once with the destruction of the bridge
This achievement requires a bit of luck and timing and ensuring that your team's health is topped up. Make sure the engineer completes the two top (or bottom) switches together and then third go for the left-hand of the remaining switches. Your team needs to be to the right of the bridge to win the level (although not necessarily to get this achievement). Get your party into a line on the right-hand-side of the bridge, keeping an eye on enemy movement ranges to make sure they can't run past you and get off the bridge. Generally the AI will face you head-on but not always. Forming a line should ensure that you end up with 4 enemy units on the bridge. Once they are there, have the engineer flip the last switch. The lost of the bridge will insta-kill the enemy units and you will get the achievement.

It's worth noting that with Cendor's Turn Back ability, the engineer can cover incredible distances. Ensure that the engineer is exactly three hexes away from a target switch. Send him to the switch. Cendor's ability will then return him to his original position, at which point the engineer can now move 3 hexes towards a different switch. This effectively gives the engineer a movement speed of 9 for hitting the switches. Very useful on this map.

Battle The Bridge: Kill a total of 40 enemies in a battle
Essentially you need to delay collapsing the bridge until this achievement pops. I found I had killed enough enemies by around Turn 17, but since it's randomly spawning it's hard to keep track.
Tips:

• Back up all the way to the bridge to give yourself time to plan for incoming enemies.
  
• Use the Ballista to stop the Skull Throwers and Shaman from reaching the fight.
  
• Try to keep unit groupings to pairs, to minimize the effect of thrown rocks
  
• Plan unit movement to utilise the Priestess' healing buff
  
• Line up on the right-hand side of catapult targets to encourage enemies to enter the fire zone.
  
• You don't have to win the level to get the achievement, it should pop part-way through.

Win the battle The Ambush in 11 turns or less

Win the battle The Origin without losing any unit
This stumped me for a while. The odds are overwhelmingly against you and the Hell Beast/Surprise Imp which spawns in the cutscene does 1-Hit KOs on most of your units, plus Azuk Junior does 8 HP with 5 HP of damage to a unit behind. In addition, your healer is way over to the left, far from your force on the right, so it's going to be a while before they get any healing.

Firstly, Cendor's Turn Back ability can turn the Hell Beast back into an Imp for an easy kill. Thanks to Farabel developer Christophe for putting me on the right track with this. Once this Hell Beast is out of the way, rush forward and try to kill as many units as possible in turns 1 & 2.

Position Cendor on the far side of the Hell Beast before reverting it and in turn 2 you can get into the middle of a group on the left and maximise lightning damage, taking out 2x Imps. On the right of the field, move forward but keep your units at the end of turn one in pairs of two side-by-side. This way you can tempt the Cave Troll to throw his rock, but he will blow it on two units instead of three and you will save yourself 3 HP damage. Position the cavalary over to the right and as far north as possible and you should be able to charge to either take out the Skull Throwers in one hit or heavily damage the cave troll.

Kill as many normal sized Goblins as you can in turn 2. In turn 3, Azuk Junior appears and he will turn dead goblins into 4 HP skeletons. These can be one-shot killed by archers but they are a drain on actions, so clear as many small units in turn 2 as possible. In the centre group, you should be able to use archers and the mage to clear out the Imps. Don't forget that the mage can summon elemental at two range AND it moves, giving a great reach. There is a lone Imp hanging back in the centre north during turn 2. When pushing forward, just make sure you don't leave any unit in range of this one. Also, if you ensure that Cendor is nice and close to the Mage when he summons the Elemental, you can use Turn Back to have the Mage summon a second elemental. This is a huge advantage as the elemental can attack Azuk Junior directly and happily tank the 8HP damage, allowing your weaker units to move in and melee without fear of repurcussion. Other than that, pull units with low HP out of range, create tempting targets with high HP units and try to maximise use of your healer. I'd recommend one Turn Back to de-evolve the Demon Imp, one to get a second Elemental and one to double up on the Priestess' healing ability.

Video of my completion of this achievement: https://youtu.be/B6Ua8aR5cAM

Battle The Origin: Kill a Hell Beast fairly
This is tough. Hell Beast/Surprise Imp has 3 Armour, so most attacks will simply bounce off. In the first turn, Cendor should be able to charge, doing 4 HP damage, plus 2 HP with the lightning. Cendor can take the first hit, due to his 1 Armour point. The unit who starts next to the beast can use his +1 to make a dent and retreat to safety. There is a nearby archer who can inflict 1 damage, but it's safer to keep him out of range as the Hell Beast will prioritise targets it can kill. Ignore the mission objective and bring your archers and mage around the bottom left to help. These are the only units which can hurt the Hell Beast, unless you get lucky with cavalry charges (although they will die instantly on the Hell Beast's turn)

On turn 2, Cendor should retreat to four spaces away from the Hell Beast. This is important, because if you get too far away, the Hell Beast starts wandering off to find other targets. At the end of the Hell Beast's turn, it will be 2 hexes away from Cendor, so every other turn Cendor can hit it for 2 HP damage with the Lightning. Bring your archers and mage up behind Cendor to chip away and you should manage the achievement. Just make sure your melee units keep the rest of Azuk Junior force off your back. You don't have to win the battle to succeed.

Unlock all the stars
Complete the secondary challenge on each main story level to unlock this. See OPTIONAL LEVEL CHALLENGES.

Kill 5 enemies at once with the Lightning ability of Cendor
The best level for this is "The Goblin Sappers", where the Lighting sword is first introduced (or lost, depending on how you are looking at the storyline!) Each of the spawning goblins only has 2hp, so a strike from the Lighting ability is an insta-kill. Consider dropping Cendor's retaliate ability so that he doesn't kill goblins who attack him. Also, use archers to clear out any Goblin snipers who may drain his health from afar. Simply wait for 5 or more goblins to walk into range, keep Cendor's HP high and drop the lightning and it should be fairly easily to one-hit kill five or more goblins. You may need to keep the priestess nearby in case Cendor is struggling to take the incoming hits.

Heal 25 HP at once with any healing ability of the High Priestess
This is best early on in the game before the Priestess' healing ability drops to 4HP per heal. With 6 points per heal, that's possible with five injured units. With only 4 points per heal, you'd need 7 units around the Priestess, which I'm pretty sure isn't possible. Make sure your units have lots a decent amount of health - rotate healthy units to the front line if need be - and navigate the Priestess into a central point in range of each of the characters.

Heal 5 units at once with the Soothing Fire ability of the High Priestess
There's a knack to this, as Soothing Fire only activates when the Priestess ends a move action. It can be done any time in the main campaign after The Bridge. You need to place 5 other characters with at least 1HP missing into a horseshoe shape, while making sure that the empty space is close enough to the Priestess for her to walk into the middle. Once the five characters are in a horseshoe, simply walk the priestess into the centre hex and she should deliver 1HP free healing to each of the five injured units.

Remove 3 HP from a unit with the Turn Back Time ability of Cendor
You can do this well or badly. I accidentally turned back time on a unit I'd just healed. D'oh. Ideally, wait for a Goblin Shaman to cast healing on an injured unit, then race up with Cendor and send them back in time to before they were healed. Just make sure to pick a unit that needed at least 3 HP fixing. You can get this achievement while completing "Strategist of The Gates of Farabel."

Restore 3 HP to a unit with the Turn Back Time ability of Cendor
One of the useful features of the Turn Back Time ability is that it can restore HP. When Cendor uses this ability, the unit will be "sent back in time" to their status and position at the end of your last turn. So, if one of your front line units takes a beating on the enemies' turn, use Turn Back to restore them to full health. That will pop this achievement.

Win a battle against humans in Classic mode
To get this achievement, open the advanced options on the Sandbox battle mode and choose Humans as the opposing side. Then win. You can combine this with "The green tide is mine" to get both achievements.

Play the Orcs
All you have to do for this one is play as the orcs in Sandbox battle. You can combine this with "Scourge of humanity" to get both achievements.

Kill 3 enemies at once with the catapult
I find the best place to get this achievement is during "The Citadel", as the narrow streets tend to cause enemies to travel together. Just bear in mind that the centre of the catapult does 8 damage, while the splash effect does 5. If you don't manage to trigger this on enemies during their approach, make a V shape with your front line of Militia and Cendor and the enemies will fill the gaps, creating a perfect shape for a catapult attack.

Kill a enemy with a counter-attack
You'll probably get this during your main play-through, but here's a tip in case you don't. Make sure Cendor has his retaliate ability. "The Goblin Sappers" is a good level for this, because there are many enemies with only 2 HP, so Cendor's retaliate should be an insta-kill. Use your archers to keep the Goblin Snipers away and simply walk Cendor into the Goblin ranks. One of them is bound to take a pop at him and he will retaliate, killing them.

Unlock the Golden Badge in Defense mode
To get this achievement, survive 8 turns in Defense mode on Hard difficulty with High Budget.
To simply get the achievement, evasion is the best approach. I spawn my entire side over to the far right of the map. I move into the corner and encourage the enemy to head to me there. Once they are near I begin circling clockwise around the edge of the map. Usually there is some natural cover which makes you hard to flank. Make sure you have a Priestess to keep everyone topped up and a Mage to summon an elemental which can run off into the enemy and distract them with a big, heavy target. Horsemen are an excellent unit for this, because they have the highest movement of any unit and can run away.

The only wrinkle I have found with this approach is that sometimes the random generator creates a human enemy all on horseback. This makes evasion very hard. To avoid this, you can either open the advanced settings and set the enemy to Goblin, or you can spawn an elemental and place it in a square with only 2 adjacent hexes. Melee units will not be able to surround the elemental and it can survive on its own for several turns. For this reason, protect your mage at all costs so that he can respawn the elemental when it dies.

Unlock the Golden Badge in Classic mode
To get the Golden Badge, you must beat Hard mode, with High Budget, over three battles. On the second battle you get half the gold again to buy reserve units. The third battle you must win with survivors only.

I can't give you a solution as the enemy teams are randomly spawned and placed. But here are some thoughts you help you maximize strategy. Personally I think the Mage, Priestess and Cendor should form the core of any battle group, although I have favoured two Patrollers over Cendor to great success, as they provide more flexibility and Cendor's ability can be circumstantial.

In the battle, you are placed at opposite ends of a large field. I recommend passing on the first two turns. The AI will come straight towards you, allowing the weaker, faster units to race out in front where you can pick them off accurately without getting hammered by heavy hitters or ranged units. The Ballista can be employed to great effect to remove Imps, Snipers and Skull Throwers before they even become an issue.

I created this table, which shows unit offence plus damage reduction (armour). The damage total is that units damage + rage multiplied by their # of attacks. The mage has a boosted total, because I added the Elemental's damage and armour to the Mage's score. I've assigned the Ballista and Catapult arbitrary Armour values of 5, because they cannot be hit.
It's not perfect, but it does demonstrate how much punch the Patroller provides for very little cost. Two patrollers deal way more damage than three Bowmen. Units like the Militia seem tempting because of low cost and the Counter+1 ability, but it encourages front-line battling with costs damage and the ability is circumstantial. What this chart doesn't reflect is just how valuable the Priestess' heal is (essential). Cendor's "Turn Back" is extremely valuable and is probably worth the extra cash, since it effectively can give you three extra Patrollers at full strength, plus has a healing ability.

I've only given the Catapult a damage rating of 18, because even though the total of 8 + six lots of 5 is 38, most of the time the AI spreads out so that you don't get 6 targets in a group. Most of the time you will be hitting three targets. I personally favour the Ballista, because it is slightly cheaper and is really most useful when the enemy deploys a Catapult, which will make your life miserable. (although at the time of writing I experienced a bug which caused the Ballista to not carry over to successive battles).

Kill 100 enemies
You'll get this easily during your first play through the campaign.

Kill 400 enemies
Unless you're really focused on objective and not killing every unit on the field, you'll almost certainly get this during your first play through the campaign.

Kill 1,000 enemies
I personally got pretty close to this at the end of my first play-through of the campaign, although I did play most of those maps twice to get the conditional victory achievement. But for most players a single play though and enough wins in the battle sandbox to unlock the other achievements will probably pop this.

Kill 5,000 enemies
This one is really going to take a while. If you're into simply grinding for victory, then bear in mind that "The Goblin Sappers" typically offers 70+ one-hit kill enemies even in a normal game. It features portals which generate 2 new goblins per round and these goblins can typically both be killed with the double action of the Scount, so really it's a matter of time and playing that level over and over. Just don't close the portals or kill the final boss. You might want to clear out the two Goblin Mages though, because they'll make your life hard. If that's a dull way of getting 5000 kills though, maybe just enjoy the sandbox battle generator and one day 5000 kills will be yours. The good news is that Steam seens to record your kills by round, so even missions you don't win or complete count towards your total.

Kill a total of 30 enemies with the catapult and the ballista
You will get this achievement on the way to completing "Destructive Siege Engines" and quite likely during the main campaign.

Kill a total of 100 enemies with the catapult and the ballista
You get access to the Catapult and Ballista on the Gates of Farabel, The Citadel and The Bridge campaign levels, as well as optional purchases in the sandbox battle mode. "The Battle of the Bridge" is a good level to grind with the Ballista as the enemies respawn every turn until you complete the objective. So, form a good defensive line and focus fire on the enemies with less than or equal to 6 hit points. Don't waste shots on weakening bigger enemies, as these won't count towards your total.

Kill 50 trolls
Sadly you don't face enough Cave Trolls in the main campaign to trigger this. "The Bridge" generates good numbers of respawning Cave Trolls and "The Ambush" features 3 Cave Trolls from the start, if you want to rack up your total with repeating levels.

Win 30 battles
There are 13 battles in the main campaign, many of which have to be completed twice to get competing achievements, so you'll almost certainly get this while getting the main achievements and unlocking the sandbox badges. If you fall short though, just keep playing sandbox matches or replaying the main campaign until it pops.

Heal a total of 250 HP with any healing ability of the High Priestess
You'll get this on the way to achieving "Famous Healer", although it will probably pop during your first play through of the campaign.

Heal a total of 1,000 HP with any healing ability of the High Priestess
The trick with racking up this achievement as quickly as possible is to always make sure you group units with low health around the priestess before activating her area of effect healing. Only actual lost hit points count towards this achievement, so even though "+6" may appear on a nearby healthy unit, it's only the HP they actually recover which contribute to this total. It's fairly unlikely you'll do this much healing during a single playthrough, so you'll need to keep playing the story missions or use the battle generator and be sure to always have the Priestess as one of your units and don't heal troops with only a few HP missing.

Win all the unlocked battles
For every level you have completed the optional objective, a side-mission will open up, by clicking on the flag above the main campaign. For these you have basic units, no Cendor or Priestess. Win all of these to unlock this Achievement.