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