Seige Formation

Hidden agenda (Start the game with this conspiracy
face down in the command zone and secretly choose a
card name. You may turn this conspiracy face up any
time and reveal that name.)
Whenever a creature you control with the chosen
name attacks, you may pay {r}. If you do, create a
token that's a copy of that creature that's tapped
and attacking, except it's not legendary. Exile the
token at the beginning of the next end step.