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