The oldest record of Fluffy’s presence is not a sighting in any conventional sense — it was not witnessed by any living being in the current era, and what is known comes from the fragmented oral traditions of the pre-Convergence world, some of which survived through the Darkmane Elves’ ancestral memory and others through Zunarorth himself.
During the final phase of the Dragon Era, as The Shadow moved systematically across the world killing every dragon it could find, witnesses — mainly surviving elf communities in the deep forest — reported seeing something in the sky above the killing grounds that was not the Shadow and was not any dragon. It moved against the Shadow’s path, not parallel to it. It did not stop the Shadow. It did not intervene. But those who saw it described the impression of something pursuing — something that was aware of the Shadow and in motion toward it, arriving always slightly too late, or not late at all but choosing not to close the distance.
Whether this account describes Fluffy attempting to intercept the Shadow, following it for reasons of its own, or simply passing through the same sky at the same time is unknown. The Shadow was not stopped. Zunarorth survived. Fluffy, if it was there, did not explain itself.
See The Five Public Appearances of Fluffy for the full account of all five sightings.