tldr; although he suffers, he will stop at nothing to stop the suffering of others

Nova is debatably the one bossfights character who has gone through the most. From the very start of his existence he floated in space with no possessions, no companions aside from himself, and no language to think in, only complete nothingness. He longed for any sort of interaction but found nothing. He knew he was a protector of sorts, but did not know what to protect the universe from, as he was the only thing alive. And when he did finally find creatures to interact with, when he finally did find purpose, they’d eventually die, or go extinct altogether. And that doesn’t even count the future, as he knows eventually all the other people in the Bossfights universe will eventually die and leave him alone once again, waiting for the universe’s inevitable heat death. …but that’s why he tries. He knows everything is temporary, and whatever shred of solace he may have will eventually wither away. He cherishes the moment, and he will do anything to keep it from dying out. This man is the definition of selfless, and will do practically anything if a life is saved from doing so. He accepts his fate to outlive everything, and he makes the tiny fraction of good moments in his existence worthwhile by making it worthwhile for others. “Defender of the universe” doesn’t just mean the universe itself, but everything inside of it.