Novice Climber, Competent Climber, Proficient Climber, and Cragsman

Summit 5, 10, 15, and 20 Fundamental peaks.


Crimp Competent and Bouldering Expert

Summit 5 and 10 Intermediate Boulders.
Some people recommend that you use coffee on these, but they are definitely possible without it.


Walker's Pillar, Great Goal, Eldenhorn, St. Haelga, and Ymir's Shadow (including Harnessed)

These achievements are obtained by reaching the summit of each respective Advanced mountain without the safety harness. As of a recent update, you should also get the five achievements for climbing them with the Safety Harness if you summit them without it. Naturally, that does not work the other way around.


OAS Member and Great Gales Mountaineer

OAS Member is achieved when you've reached the summit of roughly 33 peaks. This triggers the game's first ending. Great Gales Mountaineer is achieved for reaching the top of all 20 fundamental peaks, all 10 intermediate boulders, and all 5 advanced mountains.


The Great Bulwark of the North and The Solemn Tempest (including Harnessed)

These achievements are obtained by climbing the last two Expert mountains. I highly recommend that on your first time climbing to the top of the Solemn Tempest, you use the safety harness. You won't get the other Solemn Tempest achievement, but you will get a good idea at how long and hard this level really is. (It took me eight hours on my original successful attempt, but I can personally confirm that it's doable in about five and a half hours without rushing).


Pioneering Summiteer and OAS President

These achievements are obtained by reaching the top of every single peak in the game and watching the game's second ending.


More haste, less speed & Friendly Summits

These achievements are fairly simple. Talk to the respective character on Walter's Crag and Walker's Pillar and agree to climb with them. They'll eventually climb ahead of you and wait at the summit, but you won't get the achievement until you meet them there.

Family of Mountaineers

This one requires you to collect all of the pieces of the torn photograph. There are five of them in total. Three of them are hidden on the fundamental peaks while the other two on the advanced mountains. I know that some people enjoy finding these things themselves, so I won't go any further from that. Just know that you will be well rewarded for doing this.


Magpie of the Great Gales

For this one, you must grab every single collectible in the game. (Yes, even the annoying one on Leaning Spire). The game provides you with a map that tells you how many collectibles are on a peak next to the peak's name, so I don't really need to point out anything more.
However, if you want more exact descriptions of the locations of collectibles, I recommend this guide: https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3100249379
Edit: I think I might have wrote this section before the Barometer was introduced. You get it alongside the map and you can use it to pinpoint the exact location of a collectible on a mountain. Just keep in mind that the arrow is based on where you're looking, not where your body is positioned. That had me confused until I started looking for flowers in the DLC.


Keen Sight

This one requires you to use your monocular to spot mermaids in the background. There are seven of these spread out across the fundamental peaks. There's only one per peak with the exception of the Lighthouse which has two. All of the mermaids can be spotted from the ground except for the two at the Lighthouse and the one at the end of Land's End. The game lets you know that you've gotten these with a little jingle, but beyond that, these don't do anything outside of the achievement.

If you would prefer to know the exact locations instead of trying to find them yourself, I recommend the following guide: https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3079966403

Advanced Free Soloist and Expert Free Soloist

These achievements require you to reach the summit of all of the advanced and expert peaks without using any ropes. Unlike the other free solo achievements, you can get these two in the normal mode, so there's no need to worry about permadeath.


Walker's Pillar, Great Goal, Eldenhorn, St. Haelga, and Ymir's Shadow (Free Solo)

These are individual achievements that require you to be in either You Fall, You Die mode or Free Solo mode. You have to climb the individual advanced mountains without any rope and without falling once. If you fall, you're going straight back to the fundamentals. (It is technically possible to survive a fall, regardless of height, if you manage to grab onto a hold before you hit a flat surface hard. The chances of this happening are very low, though).


Great Bulwark (Free Solo), Legendary Free Soloist, and Death Defier

Great Bulwark (Free Solo) is fairly simple. You just got to reach the top without using any ropes. However, Legendary Free Soloist and Death Defier are more interesting. Legendary Free Soloist requires you to reach the top of the Solemn Tempest without any ropes, but you can still use the Bivouac (which is a one time checkpoint that you can save and quit from). Death Defier is pretty much the same, but you can't use the bivouac. Naturally, all of these require you to be in either You Fall, You Die mode or Free Solo mode.


Expert Cragsman, Grand Master, Alpine Master, and Living Legend (Free Solo Mode)

These achievements require you to, very specifically, be in Free Solo mode (which means no ropes, no coffee, no chalk, no nothing). The first two require you to complete all of the Fundamental and Advanced peaks in this mode. The third one requires you to complete both the Great Bulwark and the Solemn Tempest in this mode. The last one requires you to summit every peak in this mode. This mode is also permadeath, so if you fall once, you have to redo everything.


Tips:
- If you fall into water, regardless of height, that will not be counted as a death in free solo mode, allowing you to restart the mountain safely.
- Don't panic. I've lost multiple attempts because I panicked and made a very simple mistake.
- Find the right path for you. If you want to get the individual achievements incrementally without stressing about going for all of them all at once, it's a good idea to find the right combination of fundamentals and intermediates to get to the advanced mountains quickly. If you complete 15 fundamentals + 5 intermediates or 20 fundamentals + 1 intermediate, you will unlock the advanced category, but which ones you find difficult is up to the individual player. Experiment.
If you're looking for a fast pass to the expert category, reaching the peak of Ymir's Shadow unlocks it immediately, but you will not get the 10-point crampons until you reach the top of three advanced mountains, so keep that in mind.
-If you reach the peak of Old Grove's Skelf at any time, you will immediately obtain the 6-point crampons.

If you want more tips and tricks, I would highly recommend the following guide which goes more in-depth:
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3249317040

Wrath of Wally

Endure the never-ending onslaught of Wally. On a brand new save file that has yet to summit any peaks, you can activate the Wrath of Wally which makes it so that Wally appears on every single peak to peck your hands off of the holds. (for context, Wally is the relentless gull that attacks you on the Old Skerry boulder). You have to successfully reach the top of every single peak with Wally attacking you to get this achievement. This sounds like a nightmare, but thankfully you can do this on the normal mode, so you don't have to worry about permadeath. (Now that I've accidentally completed Wrath of Wally, I can confirm that you can use the safety harness. I'd recommend saving it as a last resort on Solemn Tempest, though. Especially, if you want any chance at doing the next achievement).


Skyborne

Here it is. The most sadistic new achievement that has been added to this game (so far). After completing the Wrath of Wally mode, you can activate Avian Chaos. Avian Chaos is a harder version of the Wrath of Wally mode that can only be activated in Free Solo mode. You still have Wally to deal with, but he's joined by another bird that is just as aggressive. So, now you have to deal with even more pecking while you climb mountains without any tools knowing that if you fall even once, it's game over. You must reach the top of every single peak with Avian Chaos mode enabled on Free Solo mode to get this achievement. It's ruthless, to say the least.

Don't Be Hasty and Lofty Ambitions

Take a big fall 50 and 100 times. You'll know you've taken a big fall if your character keels over and the screen goes black. This is the same type of fall that kills you permanently in You Fall, You Die mode and Free Solo mode. You should get these naturally as you play the game.


Bad luck to kill a sea bird!

Slap a sea bird 50 times. This is fairly simple. Keep one hand on a handhold, anger a sea bird, and use your other hand to whack it when it comes to peck your hands off. There's a high chance that you'll get this naturally.


One Hold Short of Madness

Reach the summit of every peak in You Fall, You Die mode. Thankfully, you're allowed to use ropes for this one. However, you can not use the safety harness at all. Also, falling too far while attached to a rope will apparently kill you, so keep that in mind. You should automatically get this if you manage to summit every peak in Free Solo mode.


Rapid Summiteer, Fleet-footed Boulderer, Pinnacle Chaser, and The Great Gales Sender

Beat the time records on every mountain. There are also handhold and rope records, but you do not need to beat those. Only the time records need to be completed. There is a high chance that if you activate the pocket-watch before the intermediate boulders that you'll get most of them automatically just by clearing them. There's also a small possibility on the other peaks as well, so once you get the pocket-watch, it's generally a good idea to keep it on so you can compare how long it took to how fast you need to be. It'll reset whenever you hit the ground, but any ropes that are still in the mountain will be automatically counted toward the rope record. Generally, coming back with the gear you get later in the game will help you breeze through all of the fundamentals and a decent chunk of the advanced.

Stamps

There's a stamp for every DLC mountain. All you need to do is reach the peak and you'll obtain it. It doesn't matter whether or not you used the safety harness or anything else. As long as you reach the top, you will get these.


Pins

There are a lot of these, so let's go in order.

Greenhorn, Journeyman, and Veteran pins are obtained by reaching the summit of all of the peaks in the DLC. Assuming you do the peaks in order, you'll get the Greenhorn pin around Old Rekkja, the Journeyman pin around the Great Silf, and the Veteran pin once you've done all of them.


The Idol Collector's pin requires you to collect all of the idol pieces throughout the DLC. These show up on the collectible map and the barometer will point to their locations on the peaks themselves. Some of them are very well hidden and require you to climb higher than them, so you can find the path back down to them, but they're not impossible to find if you keep an eye out. I would recommend the following guide if you'd prefer to not worry about it: https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3369372712
There are two pins for collecting flowers in the DLC. The Edelweiss flowers which are generally difficult to reach, but usually in plain sight, and the Gentiana flowers which are generally well hidden, but easy to reach. Both flower types show up on the collectible map and can be tracked with the barometer and the Gentiana flowers are always found under underhangs.

Here are the flowers I've found so far:

Edelweiss:

1. In the Great Bok Tree toward the end of the intended route when you're on the tree with a bunch of vines in a row, look up. It's on the very tip of the top of that tree, requiring you to crampon jump off the thin trunk at least twice to reach it. I would recommend roping to ensure your safety.

2. On the Castle of the Swan King at the very end of the climb. The flower is about 80 meters up on the tower where you complete the climb. Normally, you would need to make a blind jump to find holds around the backside of the tower and then do another death-defying leap to reach the flower, but you can use a safety rope on the wooden door next to the stamp box, jump off the tower, and easily reach it from there without being in any danger. (Depending on where you put the rope on the door, you may have to drop down and make a blind jump back to the main path if you want to complete the peak too).

3. On Ivory Granites, in an absolutely ridiculous spot above the main path on the side of the peak. I'm unsure if this is the intended way to get it, but there's a suspicious hold further up the route that could let you do an insane jump to it with a rope safely attached. However, after a ton of attempts of overshooting and undershooting the flower, I can't seem to get it. There's a bit of a lip right above the flower that makes grabbing it from above incredibly difficult, but as far as I know, unless you can make an insane jump with the perfect height, you can only get it from above. You can grab the flower from below using a hold that is a little bit past to it right next to a crack.

4. On Dunderhorn, about 443 meters up, but you have to climb above it to reach it. The area you need to drop down from while roped is very close to the top. The very last mountain goat on the entire peak is in the area. From there the barometer and some swinging shenanigans should get you this flower relatively easily.

5. On Welkin Pass, toward the very end of the climb. It's visible from the main path, but if you miss it, it'll be below you. It's right before an underhang section somewhere around 469m-496m up. There's a little outcropping next to it that you can crampon jump off, so it's easier to get at it from the side rather than from above. A rope is highly recommended if you don't want to fall all the way back down.

6. On Towering Visir, at the very last crux. Slam a rope into the wall and leap toward the left. If you don't get it on the first try, you'll probably see it if you look up on the way down. The flower is relatively easy to grab, but the climb up to it is rough. Just make sure to save a rope for the top.

7. On Eldris Wall, 1,140m up. There's a row of rocks above it that go across the side of the mountain that you can use to easily rope down to it. The problem is getting a rope up there and depending on your skill, I may recommend the safety harness as a backup if you are almost out before you get there.

Gentiana:

1. On Mara's Arch, after climbing across the underside of the arch but before leaving the underhang entirely, the flower is sticking out of a wall below the main path. Using a rope is basically required if you don't want to fall into the water as there are no holds near the flower at all. I'd recommend using the monocular to spot it from the start of the map since that makes it easier to find.

2. On Treppenwald, during the latter half of the climb after the normal collectible. I don't remember the exact location, but it shoudn't be too hard to find with the barometer from there.

3. On Quietude, It's not far after an underhang section with a bunch of clearly visible crimps in a row. I don't remember its exact location.

4. On Eijun's Folly, somewhere around 84.7 meters up, there is a flower hidden right next to the main path. It's very easy to spot by turning around right after passing it. It's close to this section where you're hopping back and forth between two walls, climbing up.

5. On Einvald Falls, right next to the source of the waterfall near the end of the climb. It is extremely noticeable, so I don't think I need to specify how high it is. You can either crampon jump from below or rope down from above, but either way, this is a cinch with a safety rope.

6. On Mhor Drium, near the top of the last mountain you climb on the main route (after the jump that reminds me of Great Gaol). It's off to the left near a section that has three volumes in a row. It's not very hidden or hard to get. If you're about to reach the final handhold, you've gone too far and the barometer will set you straight.

7. On Towering Visir, midway through the first crux. After you make the first big jump and climb to the second, you'll see it above you to your right. I'd be surprised if you missed it.

There are two pins for finding five Ghostly Goats and five Great Eagles. These do not show up on the collectible map and I do not know if they can be tracked with the barometer or not. The Great Eagles only show up during the day while the Ghostly Goats only show up during the night when you use the Idol of Sundown. Both of them require you to use your monocular to collect them, much like the hidden Mermaids in the base game. Eagles make a distinct sound and can be heard before you see them, alerting you to their presence, while the Goats glow in the dark.

Eagles:

1. On Almattr Dam, about 210m up. It flies above the valley going from the top of the dam out and back. I'm not sure if you can get it from the ground or not because I only noticed it once I was all the way up there.

2. On Mohr Druim, visible from the ground.

3. On Tutorial Tower, visible from the ground.

4. On Quietude, visible from the ground. Walk a bit out into the open and you'll see it eventually.

Credit to Pivotthepup for helping me find the last eagle.

5. On The Castle of the Swan King, visible from the ground. It may be easier to see from a little higher up and is easily missed. This one made no recognizable noise for me and I ran across the peaks in circles looking for it.

Goats:

Credit to Fracture94 for finding all of the goats.

1. From Stougr Boulder, look toward the top of the Tutor's Tower.

2. Hidden in the trees to the right around the section where the idol piece is on Treppenwald.

3. On the ground in between some trees near the Great Bok Tree.

4. On top of your cabin if you look from the Einvald Falls.

5. On top of a large mountain far off in the distance that you can see from the Towering Visir. I had to climb up past the second set of volumes before I could see it.


Speaking of the Idol of Sundown, there's a pin for reaching the summit of every single DLC peak with it activated. When you complete a climb with the idol activated, it has a unique Night Summit graphic (similar to the free solo graphic) and the collectible map will show you which ones you have completed with it active.


There are three pins related to the Idol of Cruelty. The first pin requires you to reach the summit of the Towering Visir, Eldris Wall, and Mount Mhorgorm with it activated. The second pin requires you to reach the summit of all of those and the Solemn Tempest in Free Solo mode with the Idol of Cruelty active. You don't have to do that second pin all on one save file, but if you do, you'll get the third pin (which is an upgraded version of the second).

I'm not entirely sure what the Idol of Cruelty does, but activating it deactivates the Idol of Greater Balance, so I imagine the Idol of Cruelty does the opposite of that idol, making crimps and the balance meter (used in cracks and volumes) more punishing. I'm not entirely sure since the Idol has a super vague description.