Riven of a Thousand Voices

Defender.
Riven of a Thousand Voices is dealt damage in
the form of -1/-1 counters.
Sacrifice a non-token creature you control:
Search your library for a card, reveal it, then
put it into your hand and shuffle. Any player
may activate this ability once on their turn.
Riven gets X +1/+1 counters where X is the
sacrificed cards mana value.