Here is the full list of all 18 Manafinder achievements.
Finished the Prologue
Finished Chapter 1
Finished Chapter 2
Finished Chapter 3
Finished Chapter 4
Finished Chapter 5 (S)
Finished Chapter 5 (F)
Finished Gobithia's quests
Finished Orber's quests
Finished Batho's quests
Finished Dama's quests
Finished Mar's and Sol's quests
Finished Sohralia's quests
Finished Priest Nolwenn's quests
Felled the legendary beast Leviathan
Obtained all weapons
Finished Priscila's quests
Finished Qu's quests