Here is the full list of all 15 Defense of Castle Chilly achievements.
Kill 10 Goblins
Be killed by the tutorial instructor
Explore the whole castle in endless mode
Kill 100 Goblins
Kill 1,000 Goblins
Kill 10,000 Goblins
Reach wave 4 on maximum difficulty
Reach wave 10 in endless mode
Kill an enemy archer with his own arrow
Reach wave 9 without using any spells
Land a bullseye shot during the Tutorial
Reach wave 4 using enchantments on every arrow
Make excessive use of the explosive arrow enchantment
Unlock 6 additional spells
Kill an archer with the Overlords Catapult