Whenever you cast a historic spell, create a 1/1 white Soldier creature token. (Artifacts, legendaries, and Sagas are historic.)
Whenever Alistair attacks, you may pay {8}. If you do, creatures you control get +X/+X until end of turn, where X is the number of historic permanents you control.
You choose whether to pay {8} as Alistair's second ability resolves. Notably, once it begins to resolve, none of your opponents may take actions that might change the result before it happens, such as casting a spell that destroys one of your historic permanents.