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