Here is the full list of all 15 Cellar achievements.
Finish the game without dying
Find all toys
You left the doll on level 1 after you found it
Pick the doll on level 1 after the monster appears
Escape the Cellar
Find 5 lost toys
Finish level 5 in under 7 seconds after you pick up the key
Beat level 4 without being caught by critter
Beat level 3 without being hit by blowing steam
Beat level 2 with all possible floor tiles collapsed
Find your first toy
Try to leave the Cellar by going up the stairs