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