Hey, just listing a bunch of things to remember about the game
Art is cover of LoveCrafted by Ravensdagger.
Two girls cast a summon spell for a familiar because magic school requires summoned familiars to join, but one sneaks out an older version of the typical summon spell for her best friend to use to get something special. They summon cthulhu, which decides to have some fun while there
Edit: as per suggestion by Thandrall, I am playing an artificer, biggest difference (other than ofcourse crafting) is quests and starting apprentice class

1. This one is easy to recognize but really difficult to internalize and act on so I am going to put it at the top here:
LODGE THE NON-PERMAMENT INCOME LOCATIONS
yes, permament income is very tempting and many strategy games highly incentivize permament income solutions but this game is different the difference between the number and income gained from non permament locations and permament ones is absolutely massive, your lodges are moveable (as is your tower btw) and while there is a cost to both (apprentice not moving for a turn, 30-50 mana cast) the income from those location more than makes it up.
Things to look to when picking lodge/tower locations, don't need all
-inns from city you want to befriend (if you play mentalist this alone justifies a permament lodge)
preferably two unless there is more to the location
-construction site (only until the relevant tower quest is complete, ignore later)
-stables (+1 campaign speed is very big, units start with 7 speed, which means 3 hexes of dificult terrain like forest or hills, 8 makes it 4)
-6/8 permament income locations, inns; hamlets; bridges count for one, recruitment buildings count for half a point (if they give a hiring point or reduce hiring time by one) unless you intend to recruit the units from there then it's a full point, tombs count for 3, if income from bridge or hamlet is 2 gold than two points
-10/15 non permament income, depending on domain size
-landmarks (until you get instant castle spell)
2. some masters are livable, some are helpful, some must perish in divine fire. All of them are a nuisance.
So far I met:
-monstrologist sits in a corner but can give a quest either for +20 relations or -20mana either a tier 3 orc brute (best melee unit in the game once you give him a vampire glyph) or random orc unit, i don't know maybe I got lucky so far. Mostly ignore
-golddigger asks you for money in exchange for relations, has random events as you travel that spawns outpost which spread domain, also mine gold everywhere. ♥♥♥♥ this guy, but his army is strong and it's easy to keep him friendly
-healer sits in a corner and randomly gives you blessing, very easy to be friends with. Mostly ignore
-demonologist and necromancer
Kill them. They send out stacks and trigger events which straight up destroy locations, including permament income locations.
Necromancer has undead only and his tower deals 5 death damage a turn on your troops,
Demonologist has demons and early game some humans (arsonists) his tower weakens non demon units.
Both are hard countered by guardian spells righteous and holy weapons. Righteous deals 6 more damage to undead and demons, holy weapons adds 3 damage and changes it to white, undead take 100% more damage from white damage, while demons can have 30% resistance to it, but they can also have 50% physical, 30-50% death, 50-100% elemental. Both these spells cost 12 mana to cast, and 1 mana to upkeep
3. Plonk a lodge down on sevenkeep. So far it always spawned with two inns (1 gold, 2 relations per turn) in single lodge distance, if you get lodge radius increased you might also fit the landmark there.
It's questline also spawns additional locations for some mana and research, and at tier 4 you are allowed to occupy a landmark that lets you recruit keepers, a very good unit.
In sevenkeep you can recruit militias (weak unit but zero upkeep) and buy guardian spells. Those two spells to hard counter TWO circle mages? 50 gold each on a random week in tiara's temple.
Place a militia on sleep and recheck the stock each week
Edit: I found two vials of aonir on sale there, these are 5 essence ingredients, very important as late game things will need 18 essence out of 4 ingredients so you NEED 5 essence items
Bonus points for mentalists who can take gold out of a city for relations, or death mages who can create undead or harvest souls out of them
4. Human and elf units hard counter new purity fanatics, they mostly deal white damage, and both can easily get 70%/50% resistance to that.
5. Elven rangers are really good and can be recruited at alluvyan. They start expensive, squishy and not very damage-y but can learn to give ALL your units ignore forest penalties and can swim
They can also learn rooting shot which lets you divide enemy forces and volley which is an aoe and therefore perfect for breaking enemy morale. Later there is a promotion that gives them +2 range +2 vision, and there is a building upgrade for +2 range, and there is a glyph for +2 range. So casual 11 range basic/root shot.
6. Units in alluvyan have swim, use that on workers to get those sunken ruins and magic water (also I sometimes got artifacts from harvesting magic water)
7. Lyraine at tier 4 gives human barracks it's mostly good for it's upgrades, like weekly potions, more exp, longer lasting minable locations, and most important phalanx for all human units, once you get that depending on unit composition you can add +4 or even +8 armor on all units, which is a little good.
8. East of Lyraine is AUDALE it gives you warrior hall, just building it gives you +1 stackslot to your armies, ever wonder how come other circle mages have 8 unit stacks? That's how, I cannot begin to explain how valuable this is. It has two upgrade slots and three choices:
recruit crossbowmen and +2 range on all range abilities, like meteor, but not lasers or fire breaths, it also works on abilities gained from artifacts
recruit soldiers and all units get shield (which beats the point of soldiers who start with shield) this is a pretty basic but really powerful buff since even when flanked only one attack will be a flanking attack, effectively giving all your units 2 armor
recruit scouts and +2 vision +2 SPEED for all your units, speed is how far units can move in a fight, and armies can move on the map in a turn. This is a must have
9.Some adventures can give you grimoirepages, these are must have but to many can screw over you research. I finished the game without getting hero revive or teleport because I got 4 death books randomly and it clogged up. Hovewer if you want to you can reload start of turn save when you finish research since new research projects are randomised.
I should make a list of adventures that can result in pages.
10. One notable adventure is the conclave, for me it so far spawns northwest of sevenkeep, walk in keep asking questions, 1 free adamantite ingot for your tower quest.
11. speaking of tower quests:
have 2 workers, build 5 different rooms, have a construction site in your domain, meet two city-factions, invest an adamantite ingot, do a quest
12. Landmarks are good but some are better than others and some are more difficult to get, they also usually are pretty remote of note are:
statue of Niethalf which is guarded by some dwarves and that's it, 50% itemfind
castle Meldec, short quest, a lot of undead, 20% soulfind (souls can be sold for mana and in some adventures traded for with demons, or used for crafting)
necromancers should get crypt of revenants, all undead units revive after battle.
13. Gold ingots are actually kinda useless for craftitng (as are all other items that give +1 all essence) but can be sold pretty well.
14. you can craft items, for use in later crafting it seems like all crafted items have essence point needed to make them +1, so if you make a glyph/potion out of 3 life, 3 arcane , it will have 1 life, 1 arcane, 1 of either of the two, so 1 life 2 arcane for pathfinder which is 3 life 3 arcane, this also helps discover recipies for items you found but didn't make. It also works on artifacts.
15.graverobber and soul cage items can generate wealth for you even if you don't use it.
As an alchemist/artificer souls are mostly ♥♥♥♥ since they make bad ingredients. BUT you can sell them for mana, and transmute mana into gold on a 2-1 ratio or as a mentalist steal 200 gold for -5 relations and 9 mana (remember sevenkeeps with its two inns? infinite money), remains are one gold each.

16. Speaking of mentalist, while grimoire pages and quests giving them need a separate playthrough/section/guide Sevenkeeps tier 3 quest (library) might have a guaranteed mentalist grimoirepage, if you give books back to magistrate you get random page, if you keep them, it might be guaranteed mentalist page.
17. Earthmagic is king magic, fight me
While I may gush over mentalists money making options I still think earth magic is better. All schools have some good ♥♥♥♥ to them but earthmagic takes the cake,
-earth lore turns harvestable locations into minable locations based on region. Uram Gor has a bunch of adamantite veins guarded by demons and a buch of harvestable locations that are entirely unguarded, walk in, check if there is treasure in a location to be picked up, pick it up, 9 mana, roll dice for either adamantium (non-corrupted) or crystal.
-heal completely heals a unit including undead, constructs, and 300+health tier 4 behemoths
-elemental weapon makes units deal elemental damage and apply burn, it works even when overwritten by other buffs
-dwarven vault is a tower building that can give your units greedy, that is +1 gold per battle, per unit, which is up to +8 per battle. Also loot
-shape golem is expensive, but remember free adamantium in Uram Gor? it gives shaper golems, they are really strong, also devs made the golem a construct now so it can't bleed out, nito.
They also upped upkeep 4->10 and made him not regen. So heal is more important and shaper golems are even better simce they self heal
Edit: they nerfed it again to only 1 shaper golem at a time (if I understand the patch notes) likewise all titan (tier 4) units are only one at a time, shame
Overall non-adamantite golems are nerfed hard (corrupt adamantite golem is undead and heals)
-instant castle might seem useless at first, 4 mana/turn for 1 radius domain?
It IS affected by might amplifier and it can lock down landmarks without using logdes (they tend to be poorly placed)
Each landmark gives more than 4 proficiency which means you can distibute allfire into mana rather than proficiency and still come on top
also some areas can have enough to justify them like a 2 gold bridge, 3 mana + 3 research tomb I found in uram gor
-Shaper secrets spawns a shaper ruin which is +1 grimoirepage
Spawns not reveals (enchanter can reveal)
18. DEMONS ARE STRONGER THAN TIER OR POWER LEVEL SUGGEST, FIGHT AT YOUR UNITS RISK
19. as the game progresses other circle mages will grow stronger both in army stacks, tower guards and number of spires. This means their domains will start taking up more and more space, it might be smart to remove one or two, it results in no penalties from other mages and can get you a grimoire page. If you want to do that it's best to find the main spire since killing it removes the mage (and mage related events) from the map, hovewer their armies and other spires stay under "Circle" faction but these can be removed over time. Main spire will have medusae guard enchant, spawns a medusa warrior and a medusae, they both can stun your units, so units with immune to stun, or an earthmage with summon barrier can help
20. Your starting apprentice depends on crafter class, artificer will get an earthmage, he can learn earth armor, 2 focus, 1 action point, doesn't end turn, which means you can cast this on 3 units per turn, it lasts until end of combat and gives 50% physical resistance, it's really good
21. enchantments can stack, if you have a unit, and cast elemental weapon than holy weapon, it will deal +3 white damage, deal white damage, and be able to apply burn, hovewer if you do reverse it will deal elemental damage and apply burn.
22. This is because damage buffs are different, +2 melee dmg is that, +2 white dmg is all forms of dmg (including abilities) that deal white dmg, so if a unit has a promotion that gives them +1 white damage (say goblin alchemist) and you make them deal white damage the promotion bonus damage won't apply. this can still be worth it, for fighting enemies with resistances
23. Some quests have more options to solve them or make them easier with the right units/spells,
I found elves most commonly helping, usually in some scouting, magic or beastly thing, but orcs and goblins can help too (very rare) so can dwarves. Once you unlock a grimoire page for a spell school (or maybe you need two?) you can use these magics to help out.
Death magic can deal damage to undead units before the battle even starts,
Your crafting type can also help
24. Kennels from second page of nature can give upkeep free tier 2 beasts, absurdly broken if you can build it since it requirest 9 life 6 elemental essence. Good luck.
25. Connagh can be difficult to get friendly with (unless you are guardian/mentalist) but west of the city is village quest "arising new threats" it spawns 4 armies of undead and on killing the there is an empty (probably a bug) message window that gives 20 relations with connagh
26. crystal chamber allfire siphon recipe: 2 vials of aonir, twisted horn, dwarven forgebrew
It makes landmarks give allfire
I went 108 to 164 allfire in a turn, makes instant castle even better of spell

27. Might amplifier from tier4 bastion increases ALL your domains: tower; lodges; castles; allfire nodes, by +1 radius However the place is a nightmare of forests, swamps and mountains so don't go there without movement abilities
28. northern mountains look like a horrid place to travel and they are, BUT there's a bunch of dwarven windweed that restores movement, so if you can get your stacks to ignore all movement penalties and have about 12-13 speed, you should reliably be able to bunny hop windweed from one side of the mountains to the other
29. Haunted armor is tier 3 summon that can be recruited with a landmark. It's a melee undead that can root or aoe frostibite around itself. Frostbite reduces enemy armor by 2 which is neat.
Root stops an enemy for 2 turns, do you can divide the enemy armor and eat them piecemeal.
30. Paladin is a tier 3 unit that is tankier but overall weaker than the keeper, more importantly if he dies but you win a fight he comes back, so if you have a fight where you can't save everyone, let paladins die, they will be back.
31. feeding pit recipe shield of the shield, tome of elementalist, lifegiver glyph, mountain goat glyph
32. it seems like locations on edges of the map can have better income, like hamlets or bridges with two gold instead of one.
33. Since human units can have research affinity (+2 research a turn) and militias don't cost upkeep, it might be an option to build some recruitment exp buildings in your tower, than hire a militia at a town and see if leveleups give permament research than put the unit on sleep.
34. Levelup promotions are randomized but some are significantly more powerful than others.
Morever it seems like levels 5, 10 and 15 have a higher chance of these stronger promotions
Because of this your level 15 units are going to have different skill and some are better some are worse.
Arcane library from enchantment has an upgrade to incease promotion options of all units by 1, that helps a bit
35. Hiring units in town is considering buying so shop price changes reduce the cost.
Shop is a tower building you get for helping Connagh (I think)
At base it gives 5 gold and reduces shop prices by 25%
it has an upgrade that further reduces shop prices by 25%
YOU CAN STACK 3 DIPLOMATIC CONTACTS UPGRADES TO MAKE PURCHASES AND UNIT HIRING COST NOTHING.
ANYTHING YOU BUY CAN BE RESOLD FOR IT'S REAL VALUE, THIS IS AN OVERSIGHT AND A MONEY EXPLOIT WHERE A SWIMMING/MOUNTAINEER MILITIA CAN CAMP AN UNREACHABLE AREA NEAR A CITY AND EVERY WEEK BUY FOR FREE THEN RESELL FOR MONEY
I'm not gonna submit a bug report over it by I also don't intend to use it.
♥♥♥♥♥♥ as the terrain around connagh is, it is still relatively easy to max out city (because of "arrising new threats") so this building and upgrade are pretty easy to get. I think building 1 is working as intended. So 50% buy cost reduction.
36. Wishing well is actually net positive, there is an event where you throw coins don't hear a splash, send someone down and get a chest. So far I got gold, mana or research.
37. Grey dusk vale gives you an airship, which is like a small permament tower for stripping locations too remote for lodge or castle. Hovewer it also asks you to move it every turn and the annoyance factor makes a bad investment. Must have on higher dificulties.

Places/quests/spells with potential to get grimoire pages
-Shaper ruins,
-wishing well (aparently there is more than one way to get the item to get the page, but can you get multiple pages from wishing well? to be tested)
-Connach tier 3 quest
-Seven Keeps tier 3 quest (confirm if guaranteed mentalist page for refusing to hand over books)
-Earthmaster page 3 shaper secrets (it seems other pages can also have this, the question is it random? random for all except earth 3 where it's guaranteed?) also it could you can only get one page per map this way
-revenge of a dwarf (triggered by world map event)
nighwalkers - village (to be tested, triggered by start of turn, tower event)
... more to be added
4 4 3 3 2 4 after taking out two circle mages, another two pages from the remaining two mages?
that still leaves me with 2 pages missing to complete grimoire (if that is possible)
Honorable mention to alluvyan where you can learn primordial forest from quest (mostly useless but if there is a place in your domain that will always be your domain, like melded allfire nodes you can cast it for +1 allfire generation, 25 mana so over 3 weeks to recup cost) and Seven Keeps which can sell guardian spells

Willpower is morale AND magic armor
It reduces dmg from white and death by 1 each point.
If your units take more dmg then they deal (or units near them) they will lose morale.
If they deal more damage they will gain morale
If morale is higher than max unit is confident and deals more dmg
This means ranged, aoe and dot (area of effect, damage over time) attacks can screw over enemies (or your) willpower
Remember elven rangers? if you can hit 4 enemies for 20 dmg this will cause significantly more willpower dmg than hitting one for 60 (even if that 60 kills).
As morale goes down not only do you take more dmg from some dmg types (so better use those later in a turn) you also deal less dmg and on reaching Routed (0 willpower) the enemy units starts to flee in fear not attacking (not sure about counterattacks tho). this will trigger attacks of opportunity.
Units that route (and in general) when starting a turn regain 1 morale (so route won't last forever unless you press it).
Undead and constructs have willpower but it only affects magic armor it does not go down or up
Demons can lose willpower but cant route.
Some units and items have abilities to help put down willpower, there are also promotions that can affect that.
Example:
Mountain bear (kennel->mountain enclosure) has roar which reduces willpower in 2 hex radius by 3.
3 mountain bears on the frontline should near-rout most every tier 1 and 2 enemy, while also crashing their magic armor and being decently tanky for a tier 2 unit (and free of upkeep with feeding pit)

1. written
1.1 added some points up to 30, confirmed some uncertainties, explained willpower, added revenge of the dwarf to grimoire pages
1.2 added artificer class admition and some more points into new section 3
1.3 moved all points one down and added point one, it is that important