This needs to be maxed out first.Another zone-making tool is Pit of Malice, which also prevents initiations and traps opponents.

Keep in mind that Firestorm has a 0.6 cast point for all of his talents. In general, your leveling priority of Q>W>E>R. Upgradable by Aghanim's Shard - Firestorm. Upgradable by Aghanim's Scepter - Fiend's Gate. Those who stand before the Underlord will either be crushed where they are or made to bow and pay tribute. Now when his complete force is prepared for never-ending conquest, Vrogros himself enters a realm lighted by the sun to proclaim his impending throne. A few doomed legions destined only to test the power of nations above have already crossed the chasm under his command as the first waves of abyssal invaders. He constantly tries to increase his holdings by destroying or enslaving everyone he comes across.His eyes have since gone upward because there aren't many lands available in the underground realm. Vrogros is able to summon flame and debilitating malice through the twist between worlds thanks to the weapons created by monster forgemasters of his kind and his proficiency in the arts of the Dark Rift. The territory of the ruthless Abyssal Horde and their underlord Vrogros is enclosed inside honeycomb walls that were mortared with the bones of countless slaves. The obsidian metropolis of Aziyog is well below the snaking magma fields and seething roots of dormant volcanoes, its unmatched stonework covering an unending chasm. Unknown treasures and horrors existed far beneath the earth's surface. There is no tale or song that predicts their arrival. And when we have arrived, all will burn.'

Dota underlords meta