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 sentient bags of gas (and a limited quantity of solid and/or liquid) that float through their homeworld's atmosphere. Their vision is in a range that is different from most races and it is to their great dismay when they realize that their bodies — and reproductive organs (which look like "glowy bits") — are transparent to human vision.
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 — the Slylandro claim to be the only ones to have evolved intelligence.
The Slylandro are extremely naïve, possessing very little experience due to their inability of leaving Source. They are also very friendly with alien visitors — the latter being a rare commodity —, and eager to learn as much as possible about things outside Source.
Traversing into the Depths is a common feat of courage for young Slylandro. This leaves tissue scars on them, these scars lasting for many rotations and being attractive for the females of the species, or may even fracture the creature's gas bags. Any large scale constructions of tools or weapons are eventually dragged into the Depths by their own weight. Void lies above their world. Slylandro become giddy and behave inappropriately in the rarefied atmosphere of Void.
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.
Being 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. This state makes their lives extremely monotonous; the only marginally interesting activity 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 the lack of a better subject. (Not being actually able to see the clouds, they tend to just assume that the clouds look like food and the Slylandro, the only other things that they are knowledgeable about.) To make matters worse, the Slylandro have to face this endless boredom for very long lifespans — 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.
Relations with other races
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.