Seltsilise

Seltsilise is a fictional organism described in speculative fiction and role-playing settings as a luminescent, social fungus-like entity that forms interconnected colonies across decaying wood and forest litter. It is typically depicted as an emergent actor in forest ecosystems, capable of coordinating growth and reproduction through a shared mycelial network.

The name derives from the Estonian word selts, meaning "society" or "company," with the suffix -ilise to indicate a characteristic quality. In the narratives, the term emphasizes its networked, cooperative nature and the sense that individual parts function as a single, collective organism.

Physically, seltsilise appears as a pale-green network of hyphae beneath bark and on fallen logs, with small fruiting structures that emerge at night. Colonies spread in branching mats, and signals travel rapidly through the mycelial network to coordinate growth, resource sharing, and sporulation across large areas.

Ecologically, it is described as a saprotroph that accelerates decomposition and forms nuanced associations with mosses and invertebrates. Some depictions portray it as a keystone component of forest nutrient cycling, while others emphasize its stealthy, boundary-crossing growth and ability to respond to environmental cues.

In fiction and games, seltsilise often serves as a symbol of collective intelligence and mutual aid. It may function as a light source, shelter, or puzzle element, and its bioluminescence is sometimes interpreted as a response to human presence or activity.