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