About the scorpion coming into play poisoned: "This creature is on fire." (Denotes the creature coming into play infected.)
So maybe something like: "Pyrotoxin: add X/20 poison damage to each successful attack. X = number of
you own. This creature is on fire." (Rounding is assumed.)
Or the softer variant: "Pyrotoxin: add 1 poison damage to each successful attack. This creature catches fire whenever it attacks." ("Catches fire" implying that it is, as previously stated, infected for 1 [fiery] poison damage.) This could allow room for something a little more, as this seems a bit weak compared to the other scorpions. I would suggest that whenever the scorpion makes a successful attack, it (a) poisons the opponent; and (b) is infected for 1 but gets +2|+0 ("catches fire"). It would come onto the field at 0|3, or something similar, and wouldn't catch fire until it's buffed and has made its first successful attack (i.e; deals its poison damage to the opponent). Just my two cents worth.
Also:
needs a scorpion. Nice pick