Here is the full list of all 12 Spooky Heroes achievements.
You got your first kill. Congratulations !
Destroy your first rift
Kill your first boss
Store 1000 gold in the bank
Unlock the ninth hero
Finish the game
Unlock the priest
Slay 100 enemies
Complete 10 quests
Hatch a dragon egg
Buy and equip a full plate armor
Eat 10 pieces of any food