Otrov, Venemous End

Whenever another creature dies, if Otrov, Venomous End dealt damage to that creature this turn, exile that creature with a nest counter on it instead. Then, put a +1/+1 counter on Otrov.
{x}, Remove X +1/+1 counters from Otrov: Put target creature card in exile with a nest counter on it with power X or less onto the battlefield under your control. Activate only as a sorcery.