Res Publica

You may cast Res Publica only if you control no
other Government enchantments.
At the beginning of your upkeep, sacrifice
Res Publica unless you pay {1}{r}{w}.
When Res Publica is sacrificed, destroy half the
creatures you control, rounded up.

Roman creature spells you cast cost {1} less to cast.
Whenever a creature an opponent controls dies,
create a 2/2 white Roman Hastati creature token.