Isen VI

Isen VI was an ice giant planet that was terraformed into a jungle planet. Gravity on Isen VI was at least 9 gee. (COMIC: Terrorformer)

History
Thousands of years before the 25th century, the Hyperion Rann-Korr fled the Great Inferno and landed on a barren, icy Isen VI. He hid from Rassilon's Alliance of Races, in hibernation beneath the planet. He was frozen along with his ship, and remained there for many millennia.

The Doctor took Clara to Isen VI in the 25th century so she could improve her skiing. He chose this location because the TARDIS had detected a Time Lord beacon coming from somewhere on the planet. When they arrived they found that Kano Dollar, the richest human in the time period, had bought Isen VI and was terraforming it to use as a backdrop for his upcoming wedding.

During terraforming process, the dormant ship of the Rann-Korr was reactivated. Rann-Korr hijacked terraforming technology and began adapting the planet to his own advantage, heating the planet's poles and generating seismic activity which brought lava to the planet's surface. These changes destabilised the planet's ecosystem.

The Doctor was able to lure Rann-Korr into a cyclone and freeze it, trapping Rann-Korr inside and preventing him from further impacting the planet's morphology.

Flora and fauna
According to the Twelfth Doctor, the pre-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 told Clara to beware of mortally dangerous ice-sharks.

After the planet had been terraformed it was abundant with new species of plants, trees, birds, fish, insects and other land animals. These species developed rapidly over the course of three years, due to the hyper-evolution genes which the terraforming process had placed in them. Dollar Intergalactic's genetic engineering process caused all leaves to bear dollar signs and copyright symbols, marking them as property of the corporation. The Doctor suspected that all of the planet's new species had these markings. While all of these species were intended to befriendly, Rann-Korr's meddling with the terraforming process caused many to become hostile.

Some of the species included skunkeys, a bird resembling a two-headed flamingo, a large purple caterpillar-like insect, and fish resembling sharks, turtles and jellyfish.