Keeper of Arcana

Keeper of Arcana enters the battlefield with
X +1/+1 counters and has Flying.
{2}{u}{u}{u}{u}: Each player shuffles their graveyard
into their library then puts the top 6 cards of
their library into their graveyard. Until end of
turn, target opponent may play all instants and
sorceries in their graveyard for {0}, and you may
put any number of creature cards in your
graveyard onto the battlefield. (Timing restrictions
are ignored.)