Alfabeta — 9 years ago(September 11, 2016 05:06 PM)

According to the show - nothing. At best, the closest Immortal just sucks in the dead Immortal's power. I always thought it would make sense that the quickening happens as usual, but since mortals can't handle it, it fries the mortal killer to death. I don't know. The franchise basically has no canon (accept for the stuff in the first movie), so who knows, right.