Why was black chosen as the secondary color for squirrels?

It started because it fit a card I was making in Unstable. That started the ball rolling. I think black feels like a good fit as Squirrels aren’t too far away from Rats.

Maro, Bloomburrow looks amazing, but I have one problem. I am a kitchen table player and I love creature type decks. Some decks (like my knights) regularly get new cards, but others (like my kithkin) might see a new card once a decade. For Bloomburrow, I know that rats, squirrels, and birds are likely to show up I. The future and have a ton of past cards to use, but for the types like rabbits or raccoons, I imagine they will not be supported long term. Why should I make a deck for those types?

Bloomburrow existing will make us create them more than we would of had it not existed. If volume of creature types is a core issue to you (and I get why it would be), yeah, I’d stick to the creature types that have more history with the game. But there are a lot of players who will have a lot of fun using Rabbits or Raccoons even if they have to stretch a bit (and probably play changelings).

Can I get a maybe on more legendary Rats in bloomburrow? My goal is to make a sultai Nashi deck with every legendary rat ever, but so far the pickings are slim :)

Maybe. : )

I disagree with the notion that there isn't a clear definition of "real magic". It's so concrete it's even been recorded: Twenty Black Lotuses and twenty Plague Rats.

: )

If not cute pet rats, could we at least get some nonblack lab rats? that feels resonant enough

Possibly.

Is the relentless rats ability transferable? Could Card A allow any number of Card B's in a deck?

I think the rules would allow it, but it would need flavor to make sense. The larger problem is that it creates a deck situation that might be illegal without a way for an opponent to confirm. You see five copies of Card B, but haven’t seen Card A. How do you know if your opponent has an illegal deck?

Question about the relentless rats/nazgul rule: Can a card in a deck remove or alter another's limit? Or does it have to be printed on the card itself? For example, "If X is your commander, your deck can have any number of cards named Y"?

We played around in this space in Time Spiral design and it gets mucky in the rules pretty fast.

Hi Mark, may I request a wolf card with the relentless rats/nazgul ability?

You may.

You mentioned in today's article that the Relentless Rats ability can be in any color. Was that something the Council decided right away, and if not, which color(s) did you consider keeping it in?

It’s more a tool than a mechanic, like say hybrid or double-faced. All colors can have access to all the tools.

MaRo! It's my birthday, I'd like to cash in my trivia regarding my favorite creature type, slivers. What've you got for me?

Slivers came from a fan-made set (Astral Ways) Mike Elliott designed before coming to work for Wizards. Still called Slivers they represented pieces of the hero after he got sliced trying to close an astral door. The mechanic was inspired by Plague Rats from Alpha. Happy Birthday!