Alvela's Raven Form

You may cast Alvela's Raven Form only if you
control a legendary creature or planeswalker.
Until end of turn target creature becomes a raven
in addition to its other types, gets +2/+2, flying
and "whenever this creature deals combat damage
to a player, that player discards X cards, and you
draw X cards where X is half the total power of
ravens you control, rounded down."
"Behold my creation." - Melissa