I know it's not Halloween but...

Heres my thought. There should be an event where Kalista hunts down traitors. Ex. After all she hunts traitors across Runeterra to get stronger, so shouldn't she get buffs if she kills them?

For an example if she kills The Ice Witch, every 10-15 attacks (You know how Kalista is op.) she slows the enemy 5%.

I decided that the buffs shouldn't be super good as she can carry late game greatly. What do you guys think? Should this happen in Harrowing?

(EDIT: Map could be Summoners Rift (At Night) or Twisted Treeline)