"When you get 4 takedowns, consume that health to gain an adaptive bonus of 9 attack damage or 15 ab

"When you get 4 takedowns, consume that health to gain an adaptive bonus of 9 attack damage or 15 ability power."

The new rune, chrysalis, how does it work? Hopefully it won't consume my HP right after I make the takedown and ignite is ticking or I'm in the middle of a fight or something similar.