Phyrexian Lab Rat

{b/g}: Phyrexian Lab Rat becomes a Phyrexian Rat.
Put a menace counter on it.
{1}{b/g}: If Phyrexian Lab Rat is a Phyrexian, it
becomes a Phyrexian Rat Horror with toxic 1.
Put a +1/+1 counter on it. Activate only once.
{1}{b/g}{b/g}: If Phyrexian Lab Rat is a Horror and
an opponent has three or more poison counters,
proliferate.