Archon (The Nameless City)

The Archons were a race that existed at the beginning of time. The TARDIS records claimed that they were the last of the Old Ones. They had liquid appearances with albino skin, suction cups, fins, tentacles, and claws, with heads like that of an octopus and could merge with themselves. They danced along to the Music of the Spheres, and became seriously confused with any sound that differed to what they were used to.

They were the rulers of time, and claimed to have invented the TARDIS seeds from which TARDISes grew until the ancient Gallifreyans declared war on them and wiped them out, save for seven survivors who were trapped in the Nameless City of the Great Desolation.

The Second Doctor encountered the Archons, and stopped them from stealing his TARDIS in order to launch a pre-emptive strike against the Time Lords. (PROSE: The Nameless City)

Behind the scenes
originated in Michael Scott's book series The Secrets of the Immortal Nicholas Flamel. There, it is clarified that (similar to the Osirians) they had the power to change their appearances to suit themselves, such that powerful members of the species rarely looked alike. Only three Archons are named over the course of the series, one of them only mentioned. The other two are Cernunnos (another version of whom plays an important part in the Faction Paradox mythos) and Coatlicue, the latter being a snake-like progenitor of all vampires, who therefore has obvious similarities to the Yssgaroth.