The Zetetic Elench was a Level 8 civilisation that had once been part of the Culture proper but had split off around the 4th century CE with a number of habitats, Rocks, ships, drones and humans preferring to progress differently from the mainstream Culture. 
The Elench were known for discovering intriguing things, such as ancient artefacts, new civilisations, mysterious remnants of Sublimed species, old depositories of antique knowledge, and so on. As a result, Elencher craft were often followed by ships of particularly opportunistic societies in the hope of profiting from such a discovery. 
While the Culture's aim was to remain unchanged and instead help change the lesser civilisations it discovered, the Elench preferred to alter themselves on a continual basis, incorporating aspects of the civilisations and technologies they encountered. Their modus operandi was to understand rather than overpower. 
As a result, entire Elencher fleets were reported to disappear and never return, or to return but be completely subsumed by another civilisation. In extreme cases, some ships had been found to have turned into Aggressive Hegemonising Swarm Objects.