Here is the full list of all 35 Disc Room achievements.
QUIT TO MAIN MENU WITHIN 2 SECONDS AFTER DYING
EXPLORE ALL ???? ROOMS
COMPLETE HARD MODE
SURVIVE 10 SECONDS IN EVERY HARD ROOM
EXPLORE ALL HARD ROOMS
SURVIVE 20 SECONDS IN ANY HARD ROOM
DEFEAT THE ULTIMATE GATEKEEPER USING EVERY ABILITY
UNCOVER THE GOLDEN MYSTERY
DIE FROM 4 DIFFERENT DISCS IN ONE LIFE
DIE FROM ALL DISCS
EXPLORE ALL ROOMS
DISCOVER THE FOURTH GOLDEN ROOM
DIE FROM ALL DISCS IN ONE ZONE
SURVIVE 20 SECONDS IN EVERY ROOM
WALK 10K STEPS
SURVIVE 0 SECONDS OR LESS
UNLOCK ALL 6 ABILITIES
DISCOVER THE THIRD GOLDEN ROOM
FACE THE GOLDEN CARCASS
SURVIVE 20 SECONDS IN EVERY ROOM IN ONE ZONE
HOLD DOWN FFW FOR 10 SECONDS STRAIGHT
FEED ???? 4 ????
FOLLOW THE PATH
START HARD MODE
DEFEAT THE ULTIMATE GATEKEEPER
???? THE ????
DISCOVER THE SECOND GOLDEN ROOM
DEFEAT THE PHANTOM GATEKEEPER
DISCOVER THE FIRST GOLDEN ROOM
DEFEAT THE CARNIVOROUS GATEKEEPER
END A RUN FROM THE MAP
DEFEAT AND REVIVE AN ANTIBODY
DEFEAT THE OVERGROWN GATEKEEPER
DEFEAT THE ARMORED GATEKEEPER
SURVIVE 60 SECONDS IN ANY ROOM