As mentioned before, there are two types of beings called "gnomes" in the world of Arn. One is a scholarly group akin to halflings, inhabiting and maintaining the Library of Tharkad-Keln. The other are ultraterrestrials--extraplanar beings--who have been characterized as an annoying group of pilgrims, or even less charitably, as an infection of the Prime Material Plane. It is this second type of gnome that will concern us here.
Gnomes usually appear as diminutive men with nut-brown skin and large, amber eyes. There are reports of green-skinned gnomes, and youthful females, but these are more rare. No one knows if these different forms reflect real differences within the gnomish race, or are only affectations.
Their demeanor is often perplexing, as well. They often project a knowing amusement in their interactions with other intelligent species, but can at times view even the simplest and commonplace things with child-like wonder. Unless directly threatened, they often seem blissfully unaware of dangerous situations.
No one knows on what plane the gnomes arose. Some hold that it was the elemental plane of earth itself, given their connection with that element. Others hold that they hail from an alternate material plane with a higher concentration of elemental earth. Wherever they came from, they're now a race of travelers--though the purpose of their travels is mysterious.
Gnomes go anywhere there is elemental earth. They somehow dwell within--and move and communicate through--something they refer to as "tesseract networks" within the elemental particles of earth (which as all natural philosophers know are cubic in nature). Gnomes occasionally invite other sapients into their "networks," but those who return are unable to give coherent descriptions of what they have seen.
Certain species of mushrooms represent "nodes" in the gnomish network, and are places from which gnomes emerge into our plane. Consumption of these mushrooms expands the consciousness in unpredictable ways--sometimes allowing experiences of the areas around other nodes in the gnomish network, perhaps in other time periods, or allowing direct mental communication with the intellects of the gnomes themselves. The minds of other species don't always recover from these experiences.
Despite their alien nature, gnomes are generally friendly toward other intelligent races. They will often trade gems or precious stones, though the items they desire in exchange can't be predicted. They are often skilled mages and have been known to join adventuring parties for a time, when they can find one willing to put up with their eccentricities. They go and come as they please with no explanation. Mostly, they observe with interest, as if the world was a play put on for their amusement.