Guard Type

The Guard Type (ガードタイプ) is an enemy that appears in Sonic Adventure 2 and Sonic Adventure 2: Battle. It is a model of synthetic life-forms created by Professor Gerald Robotnik as a part of the Artificial Chaos project, a series of experimental cyborg weapons based on the ancient deity Chaos which roam the Space Colony ARK.

Appearance
By default, the Guard Types are blobs of water with a grey/white and turquoise mechanical head shaped like Chaos 0's inside them. This head has the symbol of Project Shadow on its forehead, light green, pupil-less eyes and a brainstem on the bottom. However, they can pop their heads out on top of their bodies, making them look like Artificial Chaos P-1s.

Overview
In Sonic Adventure 2 and Sonic Adventure 2: Battle, Guard Types are only encountered in the last storyline, but are some of the strongest foes encountered. They are found in the following Stages:

In gameplay, the Guard Types keep their heads inside their bodies by default, causing Lock-On Missiles and the Volkan Cannon shots to bounce right off it. However, they can still be destroyed with one hit with the Punch/Propeller Punch at close range. When they spot an enemy, the Guard Types lift their heads out from their bodies and attack quickly by reaching out with long and extremely accurate tentacles in a circular pattern to stab the player, so even though some are quite slow at turning, their attack makes up for it. A tip to avoid being hit is to be behind them. Alternatively, these variants will target the player with eye laser shots.

While a Guard Type's head is out, the player can hit it to destroy this enemy with one hit. When destroyed, Guard Types award the player with 200 points and drop their power source: a Chaos Drive.

Trivia

 * In the original Dreamcast version of Sonic Adventure 2, the Guard Types' liquid bodies had a transparent effect. In Sonic Adventure 2: Battle, the transparency effect was removed, making them appear to have a more "solid" appearance.