[Aztec] City of Asps

[Nefarias]

Pretty straightfoward and obvious, though so far as I can tell hasn't been posted.

City of Asps
Land
Whenever City of Asps becomes tapped, you get (x) poison counter(s).
T: Add one mana of any color to your mana pool.

Personally, I think that one poison counter is enough, but I also think that it's too early to put definite numbers on poison counters until it's clear just how easy/difficult it is to win via poison in Aztec.

Also, is the name too punny?

CURRENT WORDING

City of Asps
Land
Whenever City of Asps becomes tapped, you get a poison counter.
T: Add one mana of any color to your mana pool.

[Necrologia]

If you're worried about the pun call it City of Vipers and mention asps in the flavor text. People should get the idea.

As it stands right now though, this is too good. Outside of the Aztec set poison never comes up, and even there there are some benefits to having poison counters. That makes this almost strictly superior to City of Brass. Having it come into play tapped would fix it, but that seems like it'd be an overcorrection, and make the card unplayably bad.

[Jacob Orlove]

Even with 2 poison counters/activation, this is probably better than gemstone mine (although drawing multiples would be bad).

[Alfred]

I suggested this land already, and it was too good, because in other formats it basically has NO drawbacks.

[Upinthe]

How about if it was "At the beginning of your upkeep"? that would mean you would have to win fast or die of poison, which would be fair in other formats?

[stolen]

It could be both, meaning in a non-poison format, you can tap it five turns in a row before losing.

[Nefarias]

How would people feel about this only tapping for B and G? Making it a poisonous Bayou of sorts:

T: Add B or G to your mana pool and you get a poison counter.