Here is the full list of all 25 TRISTOY achievements.
kill one thousand shadowblobs
rescue a prisoner
complete the game in less than 90 minutes
Jump more than 10000 times
die ten times in the trap room
die twenty times in the trap room
die fifty times in the trap room
escape with Freedan, Stayn and Ink
complete the game
kill the spider sarcophagus
kill the parasite
find 7 treasure chests
betray your friend at the end
finish the game without dying
beat the sphinx in a riddle contest
bring Milo a heart
get roasted in the iron smelt
kill Fren Gidius, Kaya and Falis
Oops!
get yourself a weapon
spend some time in the elevator
kill Maguja
use gyromantic magic
confess that you're a naughty boy
play Tristoy with a friend next to you