Here is the full list of all 11 Soulcaster achievements.
Find the soulcasting artifact.
Return the artifact to the temple.
Complete every level and beat the game.
Beat the game in less then 12 minutes.
Beat the game in less then 6 minutes.
Beat the game without touching your clone.
Beat the game without spawning more then 24 clones.
Beat the game without swapping to your clone more then 10 times.
Pass the last level with gauntlet corruption.
Pass the last level with maximum gauntlet corruption.
Unlock every other achievement.