The revenger is a level 45 tank, upgraded from any tank. It is only possible to get if you died as a tier three tank in the same server. It has to be from a player, and if you got killed by a boss, it does not count. Clicking on the upgrade will change your tank to a red circle, which moves fast, but loses its barrel(s). You will get an arrow leading to the person who killed you, along with a dot where the person is on your minimap. You can track the person, and touching him / her would instantly kill both of you. It has 2x life, and 3x speed, but all upgrade points are lost, and it can only kill the player who killed you.