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