Here is the full list of all 25 The Tarnishing of Juxtia achievements.
Slay Tralium of the Valley
Slay the Drowned Brother
Slay the Wraith Legion
Slay the Herald of the Crowned
Slay the Rotting King
Defeat His Beloved and Her Loyal Defender
Remorse, or apathy?
Slay Speck Lord Tyris
Slay Sister of Reverence
Defeat Apathia the first time you meet her
Survive a perilous elevator ride
Defeat Blade Maestro Lorentino
A precious bond, severed
Slay Shadow God Drelium and finish the game
Slay Seer & Manipulator
A twisted familiarity
Shatter your ties to these Kingdoms
Slay the Subsumed Progenitor
Received all binding reinforcements from the Weaveress
Assemble all 3 armor sets
Acquire all Relics
Forge the perfect weapon
To escape across the Void
Have a conversation with your nemesis
Finish the game without dying