Finally cleared it.

[sandwich horror]

Hey guys, when the magma body comes out, combine them and place them in the center of the castle. 4~5 units are enough. Keep increasing passives such as castle repair, corpse damage, etc. Then, control it with scout troops, destroy the enemy's spawn base, and invest in return to fly away on a rocket. I didn't know how annoying and stressful it was when I didn't know anything. I think I can stop for the next series. Good luck.