Eternal Struggle

Choose target opponent. Shuffle your library,
then reveal cards from the top of your library
until you reveal a creature card with a mana cost
6 or less. Put that card onto the battlefield and
the rest on the bottom of your library in a
random order. Then, chosen opponent returns a creature card at random with a mana cost 6 or
less from their graveyard to the battlefield.
Those creatures fight each other.