Vengeance Sphere (GZ)



"The same basic function applies here. You pick it up and when your health decreases below 25%, the Vengeance Sphere tears off to pound the offending opponent."

- Ground Zero Manual

Once a player's health has dropped below 25%, the Vengeance Sphere is triggered. Streaking off toward the user's attacker, it attempts to prevent its master's impending death by assaulting their opponent directly.

Strategies
If you are low on health and armor, it would probably be better not to attack someone who has an active Vengeance Sphere. Wait until it is no longer active and then move in for the kill.