Loki, Prince of Asgard

Flash
Evolve
{u}{u/b}{b}, {t}: Put a thrall counter on target
non-land permanent with CMC less than or
equal to the number of +1/+1 counters on Loki.
You control enthralled permanent.
At your upkeep, if you control three or more
enthralled permanents, transform Loki.