Here is the full list of all 10 Skelattack achievements worth 1,000 gamerscore.
Defeat your first human boss
Acquire the Boom-a-rib
Find your little furry, flappy friend
Set out to collect all of the history of the dungeon through lore!
Retrieve the source of the blue flame and restore the dungeon
Help Gub Gub find his lost kitty
The cyclops has lost his eye and needs your help to find it.
Find all bone broths
Collect all 4 rare metals
Beat the game with less than 50 deaths