Flowstone Kavu

The pump ability here runs the wrong direction, and that reversal is the whole pressure point of the design. Most firebreathing hands you a point of power and leaves toughness alone; this one buys each point of power by spending a point of toughness, converting a stable 2/3 into a fragile threat that only grows by cutting into its own survival. The math with menace is where it turns pointed: an attacker that can't be blocked by a single creature can pour red into the swing, since the defender is already forced to commit two bodies or eat the damage. But the scaling is short, not open-ended, and that's the tension. From a 2/3, one activation makes it a 3/2, a second makes it a 4/1, and a third takes it to 5/0 and kills it before combat resolves. So you get exactly two pumps of extra reach, and the second one leaves the body at a single point of toughness, one ping or one favorable block away from dying for nothing. The ability also curdles the moment the creature sits on defense or faces a chump, because every activation you'd want to make there just walks it closer to zero. It asks you to trade toughness for a finite burst of damage, and the closer you push it, the more brittle the threat you're pushing through.