­Rugged Prairie + Noxious Shambler

Ah, : mana fixing.

And colourless swampwalking bears that can kill little stuff for lots of black.

That's an odd one.

Well both sources are colourless; so there's that part nailed down in an helpful fashion.

The unused colours are so that part's nailed too.

How about "Kill stuff for mana fixing"? What would that even mean? Prairie-walk? Funny-land-walk?

Oh, you know what should exist? Gate-walk.

Punish mana abilties, and also grant gate walk. Why not?
Artifact - - Creatures with mana abilities have -1/-1 and Gatewalk (they cannot be blocked if the attacked player controls a gate)

Quite a fun way to punish a Llanowar Elf I guess.

Meh. Hybrid creatures have? Gold creatures have? Meh meh meh.

Make all mana wild? It's been done. Still.. that's a plausible 3 cost artifact? Or maybe not, it doesn't seem to have been done at 1-for-any without tapping. And anyway, doesn't cover the bears at all. There were some knights did it in white and black, a limited amount, could model on those?

Yeah, ok, let's do a knight of the... um.. icy hand. Or an initiate, since it seems it was them that did the mana and I misremembered.

Ok, there we go. An ice-ages theros mana creature, with -1/-1 topping.

this could be misleading. using the same symbol twice, which has different meanings as input vs. output. because the symbols are identical, it seems you are getting the same mana back. but in fact not really since you can filter into other half color.

That would indeed be the point of that ability, yes. It's pretty clear it must be usable the way you want it to be, since it doesn't do anything otherwise. So it's a teaching aid; people will learn what it means, so I can then use hybrid mana gainers all over the place later.

Has a trick in which you can respond to the ability on the stack, and wash as much mana as you want as long as you do it right now. Also has a Split Second trick, since the ability is a mana ability and can't be responded to. Funny. I'd love to see a player who had a reasonable reason for exploiting both loopholes.

The infinite wash in a single turn was intentional; not sure about the mana ability bit; but hey, if you can make use of a massively negative creature, power to you.