Art suggestion:
http://www.sxc.hu/photo/1017114Came across it while working on a card earlier. Works well here I think.
Please decrease the attack power. 7 is too much for a strategic creature like this. I would prefer 0-3 attack power actually, compared to Iridium Warden.
I agree with needing a decrease, but keep in mind that the creature is only going to live a few turns at most:
Turn 1: 5 +1 = 6 poison -> 6 hp lelft
Turn 2: use ability -> 3 +1 = 4 poison -> 2 hp left
Turn 3: use ability -> 2 +1 = 3 poison -> dead
So at best, this card gets 3 attacks unless you start shelling out for some form of healing.
Without using the ability this creature only gets 2 attacks (6 poison + 7 poison = 13 damage -> dead) unless healed. Further, even if you used a guardian angel, it would only survive +1 turn.
You could use purify, of course, but then you lose the strategic value of spreading poison.
Now for total poison spread, using the posted scheme (with no healing) you would spread 3 +2 = 5 poison before this creature dies.
So if we assume that that 5 poison is equivalent to 5 attack power, then this creature can have an attack power of about 2... factor in a limited life span though, and it should probably really be 2+ ... maybe 3 or 4?
P.S. I wish I could still vote on rating. I think this card deserves much more than a 2 star rating.