@Meddler: Can I get your opinion on this ultra-risky ultimate ability?

In working on a concept for a Dark Knight Champion (which can be found in the link above), it's been tough to get an ultimate that doesn't tread too closely to Aatrox or other berserker fighters (i.e. Tryndamere, Olaf). But I also want her to have a super-high risk/reward paradigm going on.

In trying to think up new ways to give her that kind of gameplay, I thought of the following basic design for an ultimate.

#Soul Pact Grants you a MASSIVE boost in combat capabilities, but inflicts a Curse upon you. While you are Cursed, you cannot regenerate or lifesteal and rapidly lose health every second until either you score a takedown (kill or assist) or until you die. Scoring a Takedown removes the Curse and heals you for a portion of the life you lost to said Curse. You also retain the positive benefits of Soul Pact for X seconds after the Curse is lifted.

This would basically take high-risk/high-reward and go absolutely batshit crazy with it. You would get a steroid that makes other steroids look relatively weak, but it ends up being a massive gamble. If you don't kill someone, the Curse effect kills YOU! (Namely, the Curse demands a strong soul, and if you don't give it one, it'll take yours.)

Would this kind of gameplay mechanic be allowable in League, or does the idea of ult-based suicide register as toxic gameplay?