Grapple Guardian

The Grapple Guardian is a Grenchler possessed by the Warrior Ing which stole Samus's Grapple Beam, which Samus can retrieve by defeating it. It is about the size of the dead Grenchlers seen in the beginning of the game.

It is most likely an adult Grenchler that was possessed by the mentioned Ing.

It is possible for Samus to see the Grapple Guardian from the lower area of the Sacrificial Chamber by jumping up an assortment of blocks in one area of the room. However, it will not try to attack Samus nor can it be scanned until she steps foot into the arena where she battles the boss.

Battle
Samus fights the Grapple Guardian in Dark Torvus's Sacrificial Chamber. It attacks by charging at Samus, and if its eye is agitated enough, by using the Grapple Beam to pull her into its mouth. Its only weak point is its back, which is covered by a shell and is constantly guarded. However, if Samus tricks it into grappling the electrified pillars in the room, it will be stunned and vulnerable for a short time. Once its health is nearly depleted, its shell will be destroyed and it will become slower, but it will erect a barrier of grapple energy. This barrier can be temporarily taken down by shooting at its eye, allowing Samus enough time to shoot it in either weak spot.

Logbook Entry

 * Grapple Guardian: This darkling Grenchler has absorbed the power of the Grapple Beam. It will fire the beam to snare potential meals and pull them into its waiting jaws. The beam is powerful, and can attach to most surfaces, including your armor. Its eye region is sensitive; damage in the area can induce a state of anger in the target a weak spot under the back shell is a prime target as well. When angered, it will use a special attack.

Trivia

 * The electrocution-styled death may be inspired off a secret method of defeating Draygon in Super Metroid with the Grappling Beam.
 * Grapple Guardian is the largest of the Sub-Guardian bosses. When Samus is below the arena where the Grapple Guardian is fought, each step from the creature shakes the floor above, an indication of its massive weight.
 * Oddly, if Samus tries to scan this creature while under the arena through holes in the grounds, it does not work.
 * The Grapple Guardian is possibly the only boss that can be scanned before it is able to be damaged directly.
 * Unfortunately, if the player slays the Grapple Guardian before removing the bars obstructing the portal in the Gathering Hall, they are stuck, unable to progress, and must restart.