Mind-bending Leviathan

Flying
Whenever Mind-bending Leviathan deals combat damage to an opponent, target player puts the
top five cards of their library into their graveyard.
{2}{u}: Phase (If you are being blocked you may
pay this creature's phase cost to prevent all
combat damage that would be dealt to this card,
this creature deals its combat damage to the player
or planeswalker you target unless targeted
controller pays this creature's phase cost.)