"Vegeta: This ki is from...Cumber?!
The user's appearance remains relatively the same, though their Super Saiyan Blue aura becomes more diminished as a second, malicious aura with sparks of black lightning surrounds it. Additionally, the user enters an out-of-control mindset, indicated by their eyes going blank.
Usage and power
Both Goku and Vegeta are shown to be totally berserk in the form, the corrupted Vegeta attacking Goku when he tried to help him, but interestingly avoiding attacking each other when both berserk in favor of attacking Fu. In addition, their fighting styles become less experienced and more primal, as they opt to claw and grab at Fu instead of using any focused rush attacks or energy blasts.
In the Universe Creation Saga, Fu first forces an attacking Super Saiyan Blue Vegeta to take on the form after afflicting him with Cumber's evil ki, calling it a new experiment of his. When Goku attempts to interfere, Fu ends up corrupting his Blue form as well, but the two Saiyans both end up attacking the scientist instead of each other. After failing to land a single blow, the Saiyans are hit with one of Fu's own, reverting to normal, with Fu noting that a single powerful strike would be enough to dispel Cumber's Evil Aura and that there was still room to research the form.
Video Game Appearances
SSGSS (Berserk) appears in Dragon Ball Heroes, where it was added as a form for Goku and Vegeta.