User blog comment:Mineko Charat Lucky/League and the Institute has nothing to do with League of Legends anymore(?)/@comment-7782121-20130815070803/@comment-5331854-20130815101512

These in-universe theories are very interesting and would explain almost everything. I say "almost" because Lucian wants to free the soul of his beloved, which is hold captive by Thresh. So he doesn't do that out of sport or enjoyment, he wants to end this as soon as possible, unlike Rengar/Kha'Zix who enjoys the hunt or Morgana's sadistic streak.

On the other hand, Thresh joined the League, so he's immune to death (and he has a fine reason to be in the League). Lucian has no choice in this matter and will use the League to hone his skills and observe Thresh's moves. One day, Thresh will not have the protection of the League and Lucian may or may not kill him in the most epic battle that ever occured between a black guy with guns and a demonic soul-hunter.