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