Starting out we'll go over the main story related quests that are unmissable. There are quite a few of these and of course this means that while playing through the game normally you HAVE to get these to progress so you honestly don't have to worry about them.
Of course, this game doesn't really have any super missable achievements so you can play through normally, beat the game, and then come back here to find out how to get the achievements you haven't gotten yet.
One thing you'll want to make sure you're doing throughout your main playthrough though is using your ancient power on every enemy you can, as well as going after everything in the collections tab of the game. Doing these early on will save you A LOT of time.
This one is for completing the introduction and finishing the sorting ceremony. This is early on once you get to Hogwarts and choose your house.
This one is for attending your first class. This will either be mission 3 or 4 for attending one of those two classes for your first day.
This one is for surviving the troll attack on Hogsmeade. This is after you go through those first day classes and head out to Hogsmeade with your friend of choice. We all know the only real choice is Sebastian, but that part doesn't matter for this.
This one is for meeting Charles Rookwood in the map chamber. You'll go through a few missions and on mission 23 "Percival Rackham's Trial" you'll get this.
This one is for saving a dragon. This will be a while later on during main story mission 34. You'll go through a poacher arena and eventually save a dragon.
This one is for wielding a deathly hallow. This is during the main story mission number 40 "Niamh Fitzgerald's Trial."
This one is for visiting poidsear coast. You can technically do this before main mission 41, but if you don't then you'll get it then when you have to go out to the Southeast most portion of the map.
This one is for viewing all pensieve memories. This will be during main mission 43 San Bakar's Trial. You get all of the others during other story missions, but this is where you get the last one.
This one is for subduing the lord of the shore. This you'll also get during the main mission 43 san bakar's trial. It'll be after the big graphorn fight. You can't miss it.
This one is for defeating Ranrok. This is for completing the main quest 45 "The final repository."
This one is for winning the house cup. Because we were the best student and stopped Ranrok from gaining ancient powers and taking over everything we get... 100 points! And I guess that's enough for your house to win. Easy enough.
There are 4 achievements for reaching a point in the game referred to as "The Map Chamber" early on in the main story. These are technically unmissable as well, but each one is for doing it as one of the houses. That means you'll get one of them on your first playthrough, and then you'll have to do new playthroughs to rush through and get the rest.
It takes a little bit to get through, but luckily, they give you skip button to rush through dialogue and even skip larger cutscenes.
This achievement is for completing Sebastian Sallow's relationship line. There will be 8 side quests related to this all-surrounding learning unforgivable curses while trying to cure the curse placed on his sister.
This achievement is for completing Poppy Sweeting's relationship line. There will be 7 side quests related to this where you're hunting down poachers and rescuing large beasts from them.
This achievement is for completing Natsai Onai's relationship line. There will be 6 side quests related to this where you're going around with her fighting Harlow until you finally take him down.
This achievement is for following the butterflies to a treasure. You don't HAVE to do the quest related to this to start doing these, but you do want to go to all of the butterflies as they have collection items, you'll need later on for the collector's edition achievement.
These can be tough to find naturally as they don't show up on the map until you're pretty much right on top of them.
This achievement is for upgrading a piece of gear. One of the areas you unlock during the main quest line is the Room of Requirement. While doing Deek's quest (main mission 28) "The Elf, The Nab-Sack, and The Loom" you'll gain the ability to do this. Just do the first upgrade on a piece of gear to get this.
This one is for upgrading a piece of gear 3 times with your loom in your vivarium. It just takes quite a bit of beast capturing and grinding to get all of the needed materials.
This is the last quest achievement related to Deek for rescuing the phoenix. This will be during the side quest Phoenix Rising.
This one is for beating Imelda's time in all broom races. It's not hard to do and you'll get this for going through the questline to buy broom upgrades as that takes you to all of the races. Just make sure you beat Imelda at each one and boom you'll get the achievement.
This one is for invoking ancient magic for the first time. This is something you'll get early on for using your ancient magic meter as it fills.
This one is for spending 5 talent points. You'll get talent points as you level up and you can start spending them once you reach the map chamber.
This one is for spending all talent points. This can be done once you reach the max level and then you can spend all of those points.
Speaking of being max level we also have "A Forte of Achievement" for reaching level 40.
This one will be for completing all tiers of a challenge. You can do this with any of the challenges available. Once you complete that last part of it you'll get the achievement.
This one is for reaching a combo of 100. You might think this would be hard to do, but it really isn't. Just head out to this place here in the forbidden forest. Here you'll find an old building with a single infernius sitting here. If you just start spamming it with your basic cast over and over again you can grind your way up to a combo of 100 very easily.
This one is for stunning 10 different enemies using a Mandrake. You can either grow mandrake, or buy them in Hogsmeade, but either way you get them just take a few off to some large groups of enemies and then use it to rack those numbers up. An easy way to bump the numbers up greatly is to go to a battle arena and use it on the larger waves.
This one is for defeating a total of fifty enemies using Petrificus Totalus. This is by going invisible, sneaking up behind enemies, and then hitting X, or whatever button it is for you, to defeat them with one quick and silent spell. You didn't know this could be a stealth game did you?
This one is for using Flipendo ten times to tip one cow or several. Very self-explanatory. Just find a cow which there are many little ranches around the map, and use flipendo to keep flipping a cow until you get this.
This one is for reaching the highest point in the castle, the Headmaster's upper study. In order to get up to the study you're going to need level 3 of alohomora to unlock the locks leading up there. This you'll get after you get through the side quest "The Man behind the moons with Gladwin Moon for finding and bringing him Demiguise Moons. If you need to know where they are I have a guide specifically going over the "Demiguise Dread" achievement for the locations of the Demiguise.
You'll also need to already be through the "Poly Juice Plot" main story mission where you can then go to the very top of "The grand staircase" until you get to the "trophy room" where you need to unlock the level 1 door.
Go up these stairs all the way up to this junction where you'll take a left and go to this level 2 locked door. Go through there and head out onto the balcony and up here where there will be a level 3 locked door to get through. Then through there you'll be at the headmaster's study.
This one is for defeating all enemies in all battle arenas. There are only 3 of these in the game so this isn't too hard to get done. They can just take a bit to get through all of the waves. Something to note is one of those arenas are only available if you have the Dark Arts Pack DLC.
This one is for discovering all cairn dungeons. There are 12 of these on the map and they all have some main quest or side quest tied to going through them. So this is one you'll get while going after the other achievements anyway.
There are quite a few collectible achievements, so we'll be going over all of those in the article linked below.
