Here is the full list of all 15 Xanadu Next achievements.
Defeated Galsis.
Found and translated all tabulae and memoirs.
Defeated Lorelei.
Defeated Evilwurm.
Defeated Scoltula.
Barely made it back to shore after almost drowning.
Defeated Dvorak.
Defeated Berilard.
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 Ascomoid.
Conquered another dimension.
Attained all other achievements.