Dahren-Vul, Blood Mage

Whenever another creature dies, put a charge counter on Dahren-Vul, Blood Mage.
Instants and sorceries you control cost {1} less to cast for each charge counter on Dahren-Vul, Blood Mage.
{1}{b}: Destroy target creature with power equal to or lesser than the number of charge counters on Dahren-Vul, Blood Mage.