The Nemesis Shield is a powerful forcefield which renders a Transformer totally invulnerable to damage. It is formed, along with the Matrix Cannon and Vanguard Booster, from the combination of the Red, Blue, Green, Gold and Purple Mini-Con Teams.
Playstation 2 Transformers game
After the Autobots had collected all of the Mini-Cons stranded on Earth, they learned that Cybertron was being threatened by the chaos-bringer Unicron. The Mini-Cons merged together to form three incredibly powerful weapons, including the Nemesis Shield, and the Autobots were able to destroy Unicron and end the threat to their planet.