You tear open a massive, burning rift to the Twisting Nether above a location within 1 mile. This gate yawns open across the sky, casting the land below in sickly green twilight and bathing the region in felfire and war.   At the start of each of your turns, 1d6 Greater Infernals (CR 10 Fiends) rain down, crashing into random unoccupied spaces within the 1,000-foot radius. Their impact causes a 10-foot-radius explosion (5d10 Fire damage, Dex save for half). You may designate up to ten creatures as allies during casting; all others are considered hostile.   All creatures within the area
• Take 10d10 Fire damage at the start of their turn (Dex save for half).
• Must succeed on a Strength save or be pulled 30 feet toward the rift.
• Suffer disadvantage on Concentration checks.• Treat the terrain as difficult and unstable.   When the spell ends, the portal detonates in a fel cataclysm. All creatures within 1,000 feet must make a Dexterity saving throw, taking 20d10 Fire damage and 10d10 Chaos damage on a fail (half on success). The land remains corrupted for 10 years; spells cast in the zone roll a d6 — on a 1, the spell fizzles and the caster takes 6d6 Psychic damage as fel backlash wracks their mind.