Here is the full list of all 24 Nadir: A Grimdark Deckbuilder achievements.
Defeat King in Yellow
Defeat Chernobog
Play the Saint's Blood card
Defeat Minos
Defeat Lilith
Defeat Asmodeus
Defeat Koschei the Immortal
Defeat Moloch
Defeat Abaddon
Unlock Hernan Cortes as a playable character
Earn any Desires for the first time
Earn any Idols for the first time
Unlock Vlad Tepes as a playable character
Obtain any Rare card
Defeat Feaster from Afar
Defeat Fury
Defeat the Gunnery Demon
Possess a Damned as a reward
Earn any Skulls for the first time
Earn any Relics for the first time
Defeat Beelzebub
Defeat Belzebub
Purchase any card in the shop
Earn any Filth for the first time