Here is the full list of all 15 Xanadu Next achievements.
Innately learned all skills and acquired all levels of all spells.
Found and translated all tabulae and memoirs.
Defeated Galsis.
Defeated Lorelei.
Defeated Ascomoid.
Defeated Evilwurm.
Defeated Scoltula.
Defeated Berilard.
Barely made it back to shore after almost drowning.
Mapped 100% of the game.
Found and maxed out all Guardians.
Reached max rank.
Defeated Dvorak.
Conquered another dimension.
Attained all other achievements.