Njall is an immortal viking. After an encounter with a UFO with strange purposes of it's own around the year 1000AD, he found that he, along with his best friend, could recover from any injury and did not age. The two of them spent the next thousand years getting in fights with each other because they had nothing better to do. Since they couldn't kill each other, they would raise the stakes and make it interesting by making friends with mortals so that when they went to battle they had emotional weakspots.

He's freakishly patient, likes telling old stories, is a master swordfighter, and in some versions of his story he has the ability to turn into a stone giant.

Here is Njall's character tag at Super Robot Wars Unlimited Generation Alpha, the RP with the longest name that I played him at.

And here is his application (for a different RP, but all the points still sand true)