Isen VI

Isen VI was an ice planet that was terraformed into a jungle planet.

According to the Twelfth Doctor, before the terraforming Isen VI was home to the coldest, crispest and snowiest snow in the universe. Its icy winds could strip the flesh from the body and freeze the blood in the veins.

The Doctor took Clara there in the 25th century for her to improve her skiing. The Doctor warned her to keep an eye on mortally dangerous ice-sharks.

When they arrived they found that Kano Dollar, the richest human in the time period, had bought Isen VI and was altering it to use for his upcoming wedding.

The Doctor had also picked the planet because the TARDIS had detected a Time Lord beacon coming from there. This was because a Hyperion that Rassilon had imprisoned deep beneath the planet had been released by the terraforming. The Doctor was able to freeze it before it could leave Isen VI, and restored the planet to its original icy state. (COMIC: Terrorformer)