Dronid

Dronid was a Gallifreyan colony. Its name should have been Drornid but there was a typo in a first edition of Bartholomew's Planetary Gazeteer so the rest of the universe (except the natives of Dronid) called it Dronid.

Prior to the Second War in Heaven
A Gallifreyan Cardinal once attempted to set up his own High Council on the planet Dronid. He put together an army with the hopes of overthrowing the Gallifreyan High Council. He was dragged back to Gallifrey, leaving a lot Gallifreyan time technology still on the planet. (EDA: Alien Bodies)

Faction Paradox established a base on the planet, which the Time Lords, perceiving it as a threat, attacked. Members of Faction Paradox moved en masse back to the Eleven-Day Empire. (FP: The Book of the War)

Dronid was well known for its warp-poets. (EDA: The Tomorrow Windows)

During the Second War in Heaven
The first battle of the Second War in Heaven took place on Dronid. The Enemy attempted to set up their own Web of Time opposing the one created by the Time Lords. The Time Lords attacked the planet, destroying the surface with a virus. The Relic, the remains of the last incarnation of the Doctor, where was present at the time and on the planet. (FP: The Book of the War, EDA: Alien Bodies)

The Enemy succeeded in imposing their own version of the Web of Time on Dronid, leaving it untouchable to the Time Lord's weapons. (EDA: Alien Bodies)

Behind the scenes

 * On Dronid's name Lance Parkin notes that "[i]n the note about Drornid it's claimed that I got the name of the planet wrong in A History of the Universe. The spelling 'Drornid' appears in the script which came with the video (of Shada). The spelling 'Dronid' first appeared in The Universal Databank— the joke that Lawrence is making is that so many people read the 'guidebook' without checking the facts that the name 'Dronid' stuck in the end! For the record, it's spelt 'Drornid' in A History of the Universe (p.251)."