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