Golzuna is an arthropod-like alien that is the result of an X Parasite infesting and replicating traits of presumably multiple species. Its initial appearance is identical to a normal Muzby, but it transforms into the larger, rock-armored Goliath variant after taking some damage. When that form fails, it transforms again into an even bigger, more monstrous version mostly covered in spiked black armor; the cracks on the armor glow with energy when it summons a Cross Bomb. Its face has been replaced by a mass of slightly luminescent pink flesh dotted with black spikes on its underside. This form also lacks the four atrophied limbs exhibited by its previous two stages.
Initially, Golzuna looks and behaves exactly like a Muzby; it marches towards Samus Aran and tries to smash her with its oversized hind legs. When reverted its X Parasite form, it quickly morphs into a Goliath. In this state, it still attacks with its legs, but they are charged with red electricity and cannot be parried with the Melee Counter. Its new armor makes it immune to frontal attack; Samus should Slide under the boss or Flash Shift over it as it approaches, then shoot its vulnerable head.
The fight begins properly once Golzuna transforms again; its larger size makes Flash Shifting over it slightly more difficult. In addition to the claw slamming attack, it can charge up and release Cross Bomb projectiles from its back; it usually does this when Samus gets in front of it to attack its weak point. The bombs release small energy waves in the cardinal directions (up, down, left, and right) when they explode; Golzuna's body surges with electricity before they detonate, telegraphing its impending attack. The creature is stationary and crouches slightly while releasing the bombs, allowing Samus to Flash Shift over it. The color of the bombs denotes how they act:
- Pink bombs will hover in place before exploding, and are released in one of two formations; a box or a diagonal line. Samus can avoid the former by jumping into the middle of the "box" just before the bombs detonate, but the latter will generally require her to get to Golzuna's other side, letting the boss's body block the incoming explosions.
- Purple bombs track Samus until a second before they explode. These bombs linger until they have exploded three times.
When Golzuna's health is depleted for the third time, it transforms into a Core-X. Samus can easily destroy the membrane with a single salvo from the Storm Missile, allowing her to collect the internal X and gain the Cross Bomb.
As an aside, Golzuna takes severe damage from the Shinespark, and its arena happens to be just long enough for Samus to build up a charge with the Speed Booster. The boss's body normally blocks her path, but she can charge a Shinespark in between forms (where Golzuna reverts to its X Parasite form and hovers in the air for a moment). If she can hit its vulnerable point with the Shinespark, she can instantly kill its second form and severely damage its third form.
- Golzuna's three-stage transformation is reminiscent of an event in Metroid Fusion, wherein a single X Parasite must be repeatedly defeated as it shapeshifts between a Yard, a Gerubus, and a Gold Space Pirate.
- When defeated as a Muzby and a Goliath, it reverts to a single yellow X Parasite; when defeated as Golzuna, it inexplicably becomes a Core-X. This trait is only shared with the SA-X, which likewise starts as a single yellow X mimicking a Hornoad and later becomes a Core-X after infecting Samus.