Here is the full list of all 30 Tetracosm achievements.
Beat the game
Beat the game without dying
Beat the game on mode+
Beat the game in under 2 hours
Beat the game at 100% completion
Conquer the Curtain Spire
Get a time under 20s in the waterway
Get a time under 20s in the time test race
Achieve a commendable fun
Complete the boss rush
Defeat Moka
Defeat Choka
Defeat Pyre
Defeat the Ice Kraken
Defeat Comp-LX
Defeat Gamma
Pass the test... or whatever
Defeat Ashe
Defeat Zenza
Defeat Dominus
Defeat Naught
Fix the dung shoveler's problem
Do an impressive jump
Travel between realities to find a secret
Orbit an orb
Try chilly traverse
Visit the traveling artist
Take a ride in a flying saucer
Complete the infinite dash challenge without using the dash ability
Ascend the holy podium without flight