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