Kosh date back 80 million years, to the time of the Revolt of the Data when they volunteered to be temporarily changed into bilogical data-storage units.
They are generally an odd shade of light lavender, reminding one of a purple cabbage. 2.5 metres tall, they have a bipedal vertical musculature with alternating large and small tentacles arranged around the upper tosro. The "head" consists of two flattened quatraspheres.
They have gone to elder status, just short of retirement. But instead of retreating to som hidden world, they have taken a Zen-like attitude, immersing themselves in Galactic culture and observing anything they can be invited to watch. They show up at the oddest times. Patrons of the Wortl and uplifted by the Rosh.