What was the general reception of “limitless” creatures like Shadowborn Apostle and Relentless Rats?Where would you rank them on the Storm Scale?

I’d call them a 4. I’m pretty sure we’ll do more.

Might we ever see a noncreature permanent with the Relentless Rats/Shadowborn Apostle text? Something like an artefact with a tiny effect?

It needs to be something where having a large number means something, but yes, it’s possible.

Hi Mark. Can I get a maybe for an un-card with the relentless rats/shadowborn apostle ability??

Maybe. : )

Is there an internal R&D term for the Shadowborn Apostle any number ability? And do you remember who came up with the idea originally to have any number of certain cards make up your deck?

We tend to call it “Relentless” after Relentless Rats. I give credit to Richard Garfield for the mechanic as Plague Rats inspired the mechanic although it didn’t technically have it.

Is there a reason why all the creatures that allow you to have any number of copies of them in a deck are Black? Shadowborn Apostle, Relentless Rats, and now Rat Colony.

So far they have mostly been Rats which are black.

Is the Relentless Rats/Shadowborn Apostle ability in Black's color pie? it seems much more in-color for White or Green. Is it in any color's part of the pie?

It’s not limited to Black.

Why did Shadowborn Apostle and Relentless Rats get an ability that lets them dodge the deck construction rules? It seems like a more elegant solution would've been to give them the Basic supertype; there's already support for Basic cards in the deck construction rules, so they wouldn't need to be quite so wordy if that were used.

This probably needs to go into the FAQ. The Basic supertype does not let you play more than four of the card. The five basic land are called out specifically in the tournament rules.

Okay so I've gotten different answers on this question so I figured I'd come to you because you're a WotC VIP. Does Shadowborn Apostle's ability let you have as many as you want in an EDH deck or does it still have to follow the singleton rule?

I’m not an expert on Commander. My guess is you can only have one.

Is there a reason Relentless Rats or Shadowborn Apostle cannot be Basic Creatures? It seems that basic is already a super-type meaning "can have as many as you want", so I'm curious if there is a mechanical reason prohibiting this. Alternatively, is it just because you don't want to risk confusing people?

This is a Matt question. There’s a reason we can’t (or don’t want to) do that but I don’t remember it.