Here is the full list of all 15 Invasion: Brain Craving achievements.
Recruited Red. .... ..... ....... ....
Recruited Doc Brown. Now if only we could go back in time!
Recruited Peach. She was in this castle all along, hero.
Awoooo! Awoooo! Defeated the Werecar miniboss.
Recruited Jeth.
Enter Post-Apocalyptia
Defeated 150 Unholy Dead!
Recruited Clarissa.
Recruited Blue. Ga-ry, Ga-ry, Ga-ry!
Defeated 100 Unholy Dead!
Recruited Aisha.
Defeated 50 Unholy Dead!
Defeated 10 Unholy Dead!
Defeated your first Unholy Dead!
Rerolled your game!