The Slylandro are the only known race whose homeworld, which they call Source, is a Gas Giant. They cannot travel through space due to their physiology, though they have bought a self replicating Probe ("Catalog Item 2418-B: Self-Replicating Robot Explorer Probe") from the Melnorme to explore space for them and report back to them. The Slylandro have had contact with the Precursors, the original Ur-Quan and the Sentient Milieu.
They are essentially sapient bags of gas (and a limited quantity of solid and/or liquid) that float through their homeworld's atmosphere. Their visual range is different from most races and it is to their great dismay when they realize that their bodies are transparent to human vision, revealing their reproductive organs (which look like "glowy bits").
They evolved from simple, unimodular consumers which thrived in atmospheric convection currents. Originally mindless but social creatures, they developed language to better coordinate efforts to herd their food source into dense concentrations. Source has a great biodiversity for a gas giant—hundreds of species, some producers, others consumers, hunters or parasites—but the Slylandro claim to be the only ones to have evolved intelligence.
Because of their unique physiology, the Slylandro inhabit only a 500 kilometer thick layer in the the atmosphere of Source. Ascending above this layer, into what the Slylandro call "Void", causes them to become giddy and behave inappropriately. Descending below this layer into "the Depths" can be fatal as the increasing pressure can eventually rupture a Slylandro's gas bag. Young Slylandro, in a common feat of courage, will sink into the Depths just enough to damage but not rupture their gas bags, producing tissue scars on the gas bag which last for many rotations and are thought to make the Slylandro more attractive to potential mates. However, their isolation from the outside world makes their lives extremely monotonous; one of the only marginally interesting activities they can do is watching the clouds, the wind and the lightning. Indeed, as a result of this, the Slylandro have developed over eight hundred "symbolic references" solely for the purpose of describing clouds; most of the time when they are not eating, they are talking about what the clouds look like, for lack of a better subject. The lack of excitement is compounded by the long lifespans of the Slylandro—more than twenty thousand years, as Content to Hover, a Slylandro Speaker, claims to have been a nymph when the original Ur-Quan visited their homeworld.
The Slylandro have an egalitarian society, but this, as Content to Hover comments, "doesn't stop some people from being stupid fools or jerks." Inhabitants of Source deal with bothersome individuals by simply going somewhere else on their massive planet.
Because of the limitations of their world, the Slylandro have no native construction, technology or written records. Attempts to create objects from animal carcasses are futile, as the construction becomes too massive and dives into the Depths, its buoyancy being overcome by gravity. Unable to maintain written records, the Slylandro employ long songs called History Chants, whose patterns and rhythms help prevent the record from being corrupted. Also linked to their peculiar habitat and physiology is the Slylandro Timekeeping system, based solely upon the rotation period of their planet, Source. Their units of time are the Drahn, the Drahnasa, and rotations.
Unable to leave their planet, the Slylandro have to rely on the infrequent visits of other races (which the Slylandro term "Travellers") to obtain information about the outside world. As such, they are always very friendly—if somewhat naive—when dealing with alien visitors and are eager to learn as much as possible from any new Traveller. It was this curiosity that led them to purchase a Remote Self-Replicating Robot Explorer Probe from the Melnorme and to increase the priority of the Probe's Replication behavior, inadvertently creating an ever-growing menace to space travel.
 Relations with other races
Referred to as the "Shaggy Ones" by Content to Hover, the Precursors were once close friends with the Slyandro who arrived "41 Drahns ago" and introduced them to many forms of new technology and terminology, such as "aliens", "ships", "stars" and "planets". The Precursors also gifted the Slylandro with an orbital satellite equipped with a Hyperwave Broadcaster so that they could remain in active communication wherever they were.
The Slyandro remember the Ur-Quan only in their original, "brown" state, and visited with them regularly "three Drahn ago" to the point where they became great friends.
 Yuli & Drall
While the Slylandro speaker Content to Hover offers little information about the Yuli and Drall, he does note that both races were members of the Sentient Milieu and would commonly engage in conversation with the Slyandro.
The Melnorme are responsible for selling the 2418-B: Remote Self-Replicating Robot Explorer Probe to the Slylandro in return for biological information on the Slyandro's homeworld as well as their unique physiology. Unfortunately, the Slylandro were left responsible to program the Probes themselves and accidentally caused them to replicate uncontrollably. The Melnorme, however, evaded responsibility for this by forcing the Slylandro to agree to a formal waiver of damages were such a thing to happen.
 Known individuals
- Content to Hover, a Slylandro Speaker
- Sullen Plummet, female Slylandro
- Joyous Lifting, transmits historical information about the Precursors.
 Gameplay notes
 Sources of information
Both the Thraddash and the Zoq-Fot-Pik indicate the direction from which the probes come, but not the exact star system. The Arilou, while not providing any clue on the location, hint that the Slylandro live on "a world with no surface," a gas giant. One of the probe's responses in the PC version gives the probe's position coordinates relative to the Slylandro homeworld (but with x- and y-coordinates reversed). The manual hints at the possibility of life existing on Gas Giants, stating "To date, no complex life-form has ever been found in/on a gas giant; however, research into this field has been minimal." However, only the Melnorme give current and complete information on the Slylandro.
 Relevance to the plot
Though not necessary to completing the game, the Slylandro have a self-destruct code that removes the necessity of fighting probes, reduces their overall number and allows them to be scavenged for resources much more easily. Visiting them again after obtaining the Code will slowly but permanently reduce the probability of a Probe encounter to zero, and is thus not recommended due to the inability to scavenge them anymore.