Yellow liquid first debuted in Metroid II: Return of Samus, where it appears colorless due to the original Game Boy's lack of color palette. It is non-corrosive, unlike purple liquid, so Samus Aran can wade through it without her Power Suit taking any damage. However, it is much thicker than water, which is seen in Phase 3 and Phase 7. Indeed, it is gel-like to the point of being semisolid, as it will not leak nor break its mold if a hole is found on the ground beneath it. Therefore, it weighs Samus down considerably, impairing her ability to jump and completely negating the use of her Spider Ball.
Yellow liquid is far more fluid in the official remake, Metroid: Samus Returns. Here, it is assumed to have functionally identical properties to water from later games released after Metroid II: slowing down Samus' movement speed and hindering her jumps. However, these negative effects are never experienced in a normal playthrough due to Samus nullifying them with the Gravity Suit she acquires long before finding a directly interactible pool of yellow liquid. It is possible to skip the Gravity Suit by taking advantage of certain unintended mechanics. Thus, the yellow liquid would likely impair Samus's movement if she entered it without her Gravity Suit, just like in the original game, but this has not yet been confirmed.
Source and locations
Metroid II: Return of Samus
In Return of Samus, the yellow liquid first appears in Phase 1, collected in small puddles in the tunnel leading to the first encounter with an Alpha Metroid. Hornoads live near the liquid, hopping in and out of it without a problem. On the Surface in the remake, this liquid has been replaced by standard water.
The substance is seen again in Phase 9, in a series of narrow tunnels winding upward to a massive open cavern. Samus first comes across large pools of it in the tunnels; however, some of the floors inside said pools are fake, allowing the viscous liquid to drag Samus down into the room below if she does not jump out in time. If she is in one of the higher rooms, she is at risk of falling through consecutive pools until reaching the liquid-filled hall at the bottom of the tunnel network. The large cavern itself is flooded with the liquid at the bottom, making it difficult for Samus to get out of it without the Space Jump. As previously mentioned, the liquid is extremely gelatinous, thus it is never seen leaking out from the fake floors located beneath the pools.
The origin of the yellow substance is never explored upon, though the Chozo laboratory (converted into a Metroid hive by the time Samus enters it) is found on the ceiling of the open cavern, which possibly indicates the liquid leaked from the structure above into the cavern and tunnels below. Phase 1's close proximity to Phase 9 might suggest that both sources of liquid may possibly be derived from the same source.
Metroid: Samus Returns
In Samus Returns, yellow liquid can first be seen in the background of Area 6, in the room where Samus fights the first Omega Metroid; it is seen nowhere else in the area. The room is entirely covered with bio-organic structures produced by the Metroid, and the yellow liquid is seen pouring continuously from an opening in the ceiling into a pond below.
The network of tunnels and the open cavern in Area 8 feature exorbitant amounts of yellow liquid once more, also appearing in the foreground and background. In the large cavern, the largest pool of fluid is relegated to only appearing in the background, where it can be seen flowing out freely from underneath the massive structure containing the Queen Metroid's hive. Contrary to the original game, none of the pools that Samus can enter feature any fake floors; the only floors she is able to fall through are not submerged in the substance and are made up of Pit Blocks (thus serving the same function as fake floors).
As previously stated, the yellow fluid in both Area 6 and 8 are flowing out of heavily-developed Metroid webs, and thus may be evidence that the liquid is a byproduct of the Metroid species warping their environment to suit their needs. Alternatively, due to Area 6 being located below Area 8, the yellow fluid could simply be seeping down from the latter, making the Queen's hive the source of the mysterious substance.
- The first Zeta Metroid encountered by Samus features a cutscene where the creature is shown drooling yellow saliva. It is unknown if a Metroid's spittle is involved with the production of the yellow fluid seen in Area 6 and 8.
- ^ "Spider Ball onto the small Block suspended near the yellow liquid directly below the Screw Attack Blocks you came through, then place a Power Bomb." - Metroid: Samus Returns Official Guide (Walkthrough, p. 195)
- ^ Metroid: Samus Returns, Gravity Suit Skip. Youtube (14 Nov 2017). Retrieved on May 1, 2018.
- ^ https://mobile.twitter.com/tera_wasabi/status/927841653620015106 (Japanese)
|Hazardous||Acid (Beta/Fake) • Acid Rain • Afloraltite • Dark Water • Fire • Fuel Gel • Lava (Fake/Scalding-hot) • Phazon • Purple liquid|
|Gases||Dark vapor • Industrial-grade pesticide • Meta-viprium gas • Nohadin gas • Noxious gasses • Poison gas • Talvania Gas|
|Destructible||Barnacle-like material • Bendezium • Brinstone • Cordite • Denzium • Frigidite • Glass • Grobnite • Ice • Maldium • Meltable Metal • Metroid webs • Radion • Sandstone • Talloric Alloy • Vegetation • Zebetite |
Kelbium and Zafrite
|Phazon||Red • Crystal • Black Crystal • Mass • Ore • Elite Nutrient Mix • Strain Vertigo • Phazite (Red) • Concentrated|
|Crystals||Ammolite/Witherite Shards • Black Phazon • Crystallized Fuel Gel • Crystals • Dark Sentinel • Lift • Liftvine • Light • Minerals • Phazon • Red magma • Sentinel|
|Ore||Urthic • Phazon|
|Miscellaneous||Invisible platform • Jovian steel • Liquid Resource • Liquid solution • Sand |
Vaccine "Metroid" • Waste • Water • Yellow goo • Yellow liquid