Crackling Triton

The wrinkle is the color cost on the activated ability: a mono-blue body whose only trick demands red mana to fire. Without access to that off-color, this is a 2/3 with no text worth the words, a wall that taps out and stops there. That requirement is what locks the card into a two-color shell and nowhere else. The sacrifice clause makes the damage a one-time release valve, not a repeatable engine: you cash the body in for two to any target, breaking a combat math problem or pointing the last two points at a face. So you get a three-mana Merfolk Wizard that converts into a Shock once its blocking days are behind it, paying for that late-game flexibility by surrendering both the creature and a splash of red you have to find. The design is honest about the trade. It is a body now and a removal-or-burn spell later, with the off-color requirement doing the work of keeping the conversion from being free: the red mana is the toll that prices the activation, the way a colored-mana tax on any flexible card stops the upside from being pure gravy.