Chani, Fedaykin Warrior

Whenever another nontoken creature you control attacks, create a 1/1 Red Fremen creature token with Desertwalk.
Whenever Chani attacks, you may pay {r}. If you do, choose one:
• Creatures you control gain First Strike until end of turn
• Exile the top card of your library. Until the end of
your next turn, you may play it.