Immolating Souleater

The casting cost lies about what this Dog wants from you. The is colorless, so the body slips into shells with no red whatsoever, but the firebreathing engine is paid in Phyrexian red: each pump costs a red mana or, lacking one, two life. That trade is the whole pitch. A deck without a single red source can still suit this up and swing for lethal, financing every point of power off its own life total. The math is where the design earns scrutiny: two life per +1/+0 is a steep exchange rate, the kind of bargain that looks fine when you are racing and ruinous when you are not. Phyrexian mana was built to make color a suggestion rather than a requirement, and the firebreather is one of its cleaner expressions: the body and the activation are decoupled, so the question is never "do I have red," it is "how much life am I willing to spend to push damage through." That makes it a finisher that scales with your willingness to gamble, sharpest in aggressive builds that expect the game to end before the life payments come due and weakest the moment the race tightens and those payments start mattering.