Brug Mass

The Brug Mass is a vaguely humanoid collection of many Brugs gathered around an Emperor Brug (which possesses a large eye on its back). It is the first boss in Metroid: Other M and is fought in the Bottle Ship Control Room.

Battle
Shortly after Samus and the 07th Platoon arrive in the Control Room, they encounter the corpse of a Lab Worker whose lab coat is covered in green blood. A Brug soon crawls out from under it, and Lyle Smithsonian kicks it away and begins shooting at it. As Samus starts to talk to Adam Malkovich about her assistance with the Platoon's mission, hundreds of Brugs crawl out of the walls and ceiling, gather around the Emperor Brug, and coalesce into the Brug Mass.

Initially, the Marines and Samus are unable to damage the Brug Mass. Adam then authorizes the use of both the Marines' Freeze Guns and Samus' Missiles. Samus must fire a Charge Beam shot or a Missile at the Emperor Brug, allowing the Marines to freeze the tentacles of the beast. Once a tentacle is frozen, Samus can fire a Missile at it to destroy it. At this point, the creature will begin slamming its whole body into the ground in an attempt to injure Samus or one of the Marines. It can also spin its body very quickly and jump. When both tentacles have been destroyed, the base of the creature becomes vulnerable to attack and can be destroyed in the same fashion as the tentacles. After the base has been destroyed, Samus must attack the Emperor Brug to finish off the beast. Once the Emperor Brug is killed, the remaining Brugs in the mass scurry away.

Trivia

 * The Emperor Brug and Brugs that make up the boss share characteristics with the Oculus and the unofficially named Bomb Parasites, respectively.
 * The Brug Mass was referred to as "Unidentified Life Form 27" in UK's Official Nintendo Magazine: "An early encounter with a giant one-eyed monster (Unidentified Life Form 27)".
 * This boss bears several similarities to the Gohmas of the Legend of Zelda games, another series created by Nintendo. The Queen Gohma in Ocarina of Time is particularly similar to the Brug Mass. For instance, both bosses start out by watching the protagonist as a single eye on the ceiling. Also, when each boss's main body is destroyed, their eye is revealed to be the "true" boss that must be destroyed.
 * Adam could also have authorized the use of Samus' Ice Beam, yet he let the troopers use their Freeze Guns. This may be because the other soldiers didn't have Missiles, so Samus would have needed to do all the work.
 * The Brugs may have been non-violent until provoked into self-defense by Lyle's killing of one Brug.