Here is the full list of all 15 Moonlight Minions achievements.
Beat the game on hard
Kill a boss using the meteor storm ability
Beat the game on normal
Stun 15+ enemies at once using the earthquake ability
Beat the game on any difficulty
Last 100 waves
Last 75 waves
Pick up 25+ items on a single level
Last 50 waves
Complete a map on hard without taking any damage
Kill a boss using the lightning ability
Defeat the Shelled Overlord Boss
Build 25 towers in a single level
Defeat the Dragon Boss
Build 15 towers in a single level