Sentry Bot

Sentry Bot

Artifact Creature - Robot | Power/Toughness: 2 / 5 (CMC 5)
Flash
This spell costs less to cast for each creature attacking you.
When Sentry Bot enters the battlefield, you get for each creature attacking you.
At the beginning of combat on your turn, you may pay . If you do, put a +1/+1 counter on each creature you control.