Here is the full list of all 38 Thymesia achievements.
Finish "Sea of Trees" level.
Defeat Odur.
Unlock a plague weapon for the first time.
Start recalling for the first time.
Finish the tutorial.
Rest at the beacon for the first time.
Dead for the first time.
Reave a plague weapon for the first time.
Defeat Varg.
Defeat The Hanged Queen.
Defeat Corvus.
Defeat Urd.
Defeat Mutated Odur.
Defeat God of the Fools.
Defeat Sound of the Abyss.
Reach the "Chaotic Power" ending.
Reach the "Power of Vile Blood" ending.
Reach the "Blessing of Pure Blood" ending.
Reach the "Harmonized Force" ending.
Reach the "Power of Cleasing" ending.
Finish "Royal Garden" level.
Finish "Hermes Fortress" level.
Finish all levels.
Craft a potion recipe for the first time
Fully upgrade a plague weapon for the first time.
Fully upgrade a potion.
Collect all potion ingredients.
Craft all potion recipes.
Unlock all plague weapons.
Collect all lore.
Collect all story bits.
Collect all entries in the collection.
Empty the first health bar of Varg in the tutorial.
Defeat any boss without using potion.
Break 1000 barrels.
Reach max level.
Reach all endings.
Unlock all achievements.