Dark spell factory/ spells
The dark spell factory can be built at TH7
lvl1 Dark spell factory: Cost:2mil elix, spell: hell hound, Cost 100 dark elixer, summon 2 reinfocment troops called hell hounds who can jump walls and target cc troops they are too fast for traps an can jump high nough to attack air troops. If there are no cc troops they will target heroes. Hell Hound HP: 400, dps 45. (lvl 1: 2 hounds, lvl 2, 3 hounds, lvl 3, 5 hounds.
lvl 2 Dark spell factory (TH8): spell: Illusion, cost 200 DE: Troops in effected area appear to be duplicated to confuse defensive towers (lvl 1: up to 3 troops, lvl 2 up to 5 troops, lvl 3 up to 8 troops).
lvl 3 Dark spell factory (th9): spell: Royal cloak: cost 300 DE: Troops in effected area become cloaked for a brief period of time. (lvl 1: 2seconds, lvl 2: 4 seconds lvl 3: 6 seconds)
lvl 4 Dark spell factory (th10P: Spell: Whirl Wind: Cost 400 DE: Affected area causes a whirl wind powerful enough to damage enemy structures, blow away enemy troops and defelct oncoming fire for a brief period of time. (lvl 1: 3 seconds, lvl 2: 6 seconds.)
Upgrade costs are up in the air for each spell. This is the best I could make up off the top of my head.