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