If you control no monsters, select 1 monster in your opponent's Graveyard. Special Summon it. During the End Phase of this turn, give control of that Special Summoned monster to your opponent. The monster cannot be Tributed, or used as a Synchro Material Monster, while it is face-up on the field.
Revive a high-leveled monster from your opponent’s grave which you can use with Unibird to revive one of your Synchro monsters. This works because Unibird’s effect does not count as a tribute or a Synchro summon.
Use effects that can destroy or send to the graveyard monsters on your side of the field to make sure the revived monster does not return to your opponent.