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