Hellfire

Hellfire is a channeled PBAoE Demonology warlock spell, which ignites the surrounding area, dealing an equal amount of Fire damage to the Warlock and to all nearby enemies.

Tips and tactics
This is a great spell to use with an experienced healer, if you're not being focused on, and in large groups of enemies. Once started you deal out tremendous damage but also receive as much. Compared to other AoEs, Hellfire is incredibly mana efficient, not taking into account the mana needed to heal. A popular combo is warlock/priest since Power Word: Shield minimizes channeling time lost, and if combined with other AoEs, mobs die fast and the warlock is never in danger of dying.

Warlocks are unable to resist the damage that Hellfire does to themselves.

If you predict a Cat Druid's or Rogue's attack, you may break his stealth with a timely use of Hellfire.

Trivia

 * Hellfire is a basic Warlock spell in Hearthstone. The flavor text reads: "It's spells like these that make it hard for Warlocks to get decent help."