Venofax

Venofax was a planet with avocado seas.

In the first few weeks of Clara Oswald's time working at Coal Hill School, she remembered going to Venofax. (PROSE: Normality)

History
Venofax was originally inhabited by the Venofaxons.

Long after the Venofaxons went extinct, a team of archaeologists led by Professor Penelope Holroyde came to Venofax on the SS Howard Carter. The team spent months draining the water out of an area in the Ocean Peninsula so that they could excavate the ocean floor and learn more about the Venofaxons. The Eleventh Doctor and Clara Oswald visited the dig and helped them out. However, Clara got bored after a few hours and pressed a few buttons on the team's equipment, accidentally reversing all the work that had been done and flooding the site.

With the entire expedition ruined, the archaeologists left. The Doctor and Clara went to Earth in 1963 and encountered the Shroud. When the Shroud attached itself to the Doctor's mind, he piloted the TARDIS back to Venofax, where the Shroud was weakened by the anti-depressant properties of the avocado seas. The Doctor then trapped the Shroud in a worm loop around Venofax.

While the Doctor believed that the Shroud would be permanently trapped around Venofax, it had escaped by 3006. (PROSE: Shroud of Sorrow)