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