Infernal Shen

Infernal Shen and other nontoken creatures you control enter the battlefield with a shield counter on them.
When Shen attacks, put a shield counter on another target attacking creature you control without a shield counter on it, then you may pay {b/r}{b/r}. If black mana was spent, creatures you control with counters on them get +2/+0 until end of turn. If red mana was spent, creatures you control with counters on them gain menace until end of turn.