Spider Guardian

The Spider Guardian is a Darkling Pillbug possessed by the Ing which stole Samus's Spider Ball, which Samus retrieves by defeating it in the Sanctuary Fortress.

Battle
Samus fights the Spider Guardian in the Sanctuary Fortress. The Spider Guardian does not actively attack Samus, and instead moves along an extensive, labyrinthine Spider Ball Track while shielding itself with a damaging magnetic field. Morph Ball Bombs merely weaken its shield, and it can only be damaged by forcing it to collide with electric fences. To do this, Samus must weaken the Spider Guardian's shield until it turns green, then activate the Bomb Slots in the correct order so that an electric fence is turned on and the Spider Guardian's path is directed towards it.

The Spider Guardian is generally considered to be one of the hardest bosses in the game, along with the Boost Guardian and the Emperor Ing. The reason for this is the great amount of damage the charged "aura" can deal to Samus upon contact, limited amount of energy recharging, the sometimes unpredictable patterns the boss moves in the last phase (with a tendency to get in way), and the need to do precise Bomb Jumps within a very tight time limit in the last part of the fight.

Logbook entry

 * Metroid Prime 2: Echoes: "This darkling Pillbug has absorbed the power of the Spider Ball. It can travel over magnetically charged surfaces at will. The creature seems to have a connection to the local energy system. Aggravating it may cause disruptions to the system."

Trivia

 * The Spider Guardian is the smallest boss in the Metroid series.
 * The Spider Guardian and Bomb Guardian are the only guardians to not be fought on Dark Aether.
 * The Spider Guardian is one of only three bosses in the Metroid series that is "fought" in Morph Ball mode, the other beings are the Caretaker Class Drone and in some ways the Power Bomb Guardian.
 * The Spider Guardian's aura strongly resembles the death ball.
 * The Spider Guardian can only be scanned before the battle begins since, once battle starts, Samus cannot come out of the Morph Ball mode. Samus can only scan it while it runs along a Spider Ball Track in the room prior to the fight.
 * If Samus attempts to exit the fight with the Spider Guardian by going to where she entered the battle, and opens the door, the game will crash.
 * The Phazon Pillbug, a corrupted Pillbug from Metroid Prime 3: Corruption resembles the Spider Guardian.