Valerica's Diabolic Gateway (10th Level)

You draw an incredibly complex circular rune on the floor with the chalk you used as this spell's material component, you then surround it with the objects taken from the abyss that was used as this spell's material component, finally you drop the blood that was used as this spells material component in the center of the rune and speak a word of power which tears a hole between the plane you are currently on and the abyss.  

A portal opens in center of the circular rune which demons of all shapes and sizes spew out in a chaotic fury. For every minute you concentrate on this spell, 4d6 Quasits, 2d4 Vrocks and 1d3-1 Hezrous come out of the portal. They are friendly to you and your allies but hostile to every other non-demon. Each demon that comes out of the portal uses the dash action and all its speed(s) to move to the nearest non demon within 6 miles (not including creatures which they are friendly to) and attack it. If you end concentration, willingly or unwillingly, the portal closes, the demons summoned by this spell become hostile to you and your companions but return to the abyss in 1d6 rounds. If you concentrate on this spell for its full duration, the portal becomes permanent, only closing if dispelled by a 10th level or above casting of dispel magic or if 77 liters of holy water are poured onto it within 7 rounds of each other, the summoned demons increases to 6d6 Quasits, 4d4 Vrocks and 1d6 Hezrous a minute and the demons attack nearest non-demon that it is not friendly to anywhere on the world that the spell was cast on.

The casting fails, the spell is wasted and every non-demon within 60ft of you (including you) takes 6d6+66 necrotic damage which can't be decreased in any way if this spell is cast in the abyss.