Just got my deck opened up and I see this card, Speed Sigil (shadows) with persistent ability: “the first creature played each turn enters play ready”.

For Mars creatures in my deck (it’s persistent not an action so don’t need to activate Shadows) who “enter play stunned”, is this basically saying drop the first one ready/stunned and then exhaust to clear it ASAP, or is ready meaning stun free as well?

This seems like an interesting combination to proc on.

So the mars creature you’re referring to would NORMALLY enter play stunned AND exhausted.

With speed sigil in play, he would enter play stunned and ready.

Remember this first creature effect applies to your opponent too

If a card doesn’t reference stun then it doesn’t effect stun. Speed Sigil just says it enters play ready. It doesn’t say the creature is unstunned as well.

Speed Sigil can be a double edged sword...