Here is the full list of all 25 Chants of Sennaar achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Leave the Armory with the wrong disguise once the Call is made
Meet Bards in the Library
See the captured monster in the Laboratories
Ring the Abbey bell three times
Reaching the real end of the game
Finish the game (or not?)
Take a trip in the Alchemists' cable car
Attend the Bards' show in the Fortress
See the Great Door of the Abbey open
Meet a Serf in the Abbey
Rebuild all links in the game
Visit the revived Abbey Garden
Rebuild half of the links
Rebuild a first link
Validate all glyphs in the game
Activate all Terminals
Reach Exile
Fill in the Journal's first page
Reach the Abbey
Reach the Frontier
Reach the Garden
Reach the Galleries
Validate half of the game's glyphs
Discover the Preacher's corpse
Winning at both games in the Gardens