Demonic Will (魔王の意地) is a powered-up state used by Dabura to achieve high power.
Dabura utilises his full power when Gohan asks him to use his true power in their battle: when Gohan appears to be outmatching Dabura, he tells Dabura that he wants to see his true power. So, Dabura powers up using his Demonic Will to become Gohan's equal. The electricity used in the anime is blue.
Video game appearances
The power up is used as a transformation in the video games Dragon Ball Z: Budokai 2, Dragon Ball Z: Budokai 3, and Dragon Ball Z: Infinite World. When Dabura uses the Demonic Will, a black, electric aura surrounds him (it is red in Budokai 2). Only at this level is Dabura able to perform his Ultimate Attack, the Darkness Sword Attack. During the end of Dragon Rushing, Dabura will make a powerful kick in the stomach of the opponent, then kick them down to the ground with massive force while not powered-up by Demonic Will. If powered-up, Dabura will launch a blackish-red energy sphere at his opponent.