Another for the “unique use of mana” prompt. I’m not sure how valid this one is, I was thinking of also making it so B didn’t empty from the mana pool, but I was worried that might be too powerful. On the other hand, not doing that means you’re unlikely to be able to use mana from other people attacking you. Bug or flavorful feature?
Without the B staying in the mana pool, this is pure downside. You can’t gain life, you can’t add mana conventionally, and the new mana source is only usable for instants – which isn’t normally a black space. Am I missing something?
The last ability grants your mana-producing permanents “T: add BB to your mana pool. You lose 2 life.”