Mages have Greater Pyroblast, and I was thinking why not give Warlocks Greater Chaos Bolt just for shi.ts and giggles?
Greater Chaos Bolt (Resource cost: 5 Soul Shards); Cast Time: 10 seconds
Drains all the life in a 30 yards radius around you, channeling a massive chaos bolt to hurl at your target with devastating power, inflicting 216.230 Chaos Damage and ignoring all shield and protection effects. Damage is further increased by your Critical Strike Rating. If the target is a player, inflicts 80% of their total HP in Chaos Damage. The spell can not be interrupted, but an interrupt will hasten it’s cast time to 5 seconds and it will instead inflict 40% total HP damage to the target.