Sponge Tank Ult: Self-Destruct
Rage meter instead of a mana/energy bar.
Option A) The tank self-destructs dealing damage equal to health consumed.
Option B) The tank self-destructs dealing double the damage he's received in the last 5 seconds.
Both option A and B cost 60%/75%/90% of his current health.
Passive = His rage functions as damage mitigation, up to 15% at 100 rage (20% mitigation for his ult, ult only gets mitigation at 100 rage).
Update: All abilities cost rage to cast. Can only get rage by auto attacking and receiving damage.