User blog comment:Care Level/Sivirelia's Reverie/@comment-5514182-20131014170741

Bonus Passive on R: Sivir gains % Bonus gold on Kill or Assist while the Ultimate is active.

Or

Bonus Active on R: Sivir marks a target champion, if that target is killed, everyone assisting in the kill gains bonus gold.

It'll fit her new bounty hunter lore, and using the ult to chase down enemies fells strong.