Krovmir Apprentice

Painborn (Each 1 life you pay while casting this
pays for {1}. It enters the battlefield with a -1/-1 counter on it for each 1 life paid this way.)
{b}{b}, Remove any number of -1/-1 counters
from Krovmir Apprentice: For each counter removed this way, you may move a -1/-1
counter from another creature you control
onto Krovmir Apprentice.