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