Israfel, Seventh Angel

When Israfel, Seventh Angel dies, create a 7/7 Alpha creature token with "If this creature or another creature you control named Beta would leave the battlefield while the other is still on the battlefield, regenerate it instead." and a 7/7 Beta creature token with "At the beginning of the end step, if you control this creature and a creature named Alpha, exile them, then meld them into Israfel, Seventh Angel."