Detonate is a threshold Magic ability. When activated the player summons a ball of energy. The longer the ability is maintained, the more powerful the explosion will be. This ability can be maintained for up to 12 seconds and using it a second time will trigger the explosion, which hits all targets within the 5x5 area of the player. After charging for 12 seconds, an arrow animation on the floor will point towards you to show it is fully charged.
Jagex has changed Detonate so that when you are in the charging position long enough your adrenaline will be drained at the same rate as if you were standing still out of combat. Players should be careful where they use this ability, as they must maintain the charge to get the full power of the attack. This leaves them open to attack, which can result in a quick death in some scenarios.
The highest observed single hit with Detonate is currently 10,000 as on an ice strykewyrm with the right equipment. The maximum hit on an Ice strykewyrm is 10,000 anyways, which implies that Detonate is able to hit even higher.