Low on energy, creativity, and time (DARNED COMPUTER), so here's some random stuff.
In case you're wondering, the robot is one Dis Astranagant, one of the most powerful robots from the Super Robot Wars games (click the Super Robot Wars Sunday tag if you're curious). Why is it so powerful?
Because it's powered by the souls of the dead.
To be fair, the Ideon, which was a robot from an anime that appeared in the games, was powered by the force of unborn souls (or something-it's kinda hazy like so many anime), so it's got precedent. But whatever.