Siccati

The Siccati were a race of artists that venerated beauty above all other considerations. Their homeworld was Sedna, but a few moved to a colony on Neptune. (PROSE: Neptune, Sedna)

A Siccati was taken to the Realm of Light with Gordon Conall Lethbridge-Stewart to aid in the fight against the Nixxine Horde. (PROSE: The Man from Yesterday)

Behind the scenes
The Siccati originate from Andy Frankham-Allen and Richard Dinnick's 2000s fanseries Doctor Who: The Legacy. They appear at the end of the second season as a member of the Galactic Federation in 2501 and in the fourth season story Remembrance of the Time Travellers the Doctor and his companion mention encountering a group of "oddly infectious" Siccati.