Although the Kulan are essentially a rather basic race compared to some of the foes that The Doctor has fought, they are nevertheless a significant adversary as they were the first foes fought by the Eighth Doctor after the TARDIS was restored to him following his century of amnesic exile on Earth after the destruction of Gallifrey (“The Ancestor Cell”).
Possessing two hearts, purplish-red blood and slightly translucent skin compared to humans – while also being far more thick-skulled and durable, one Kulan surviving a fall that would have killed a human without injury , the Kulan relied on mental power to control their ships, as well as using magnetic induction as a power source. Although not driven by conquest for conquest’s sake, they were determined to plunder the resources of other worlds after exhausting their own homeworld’s resources, commonly nuking major population centres before their forces appeared en masse. Their society was divided between the military, religious and economic classes, with a representative of each making up the Committee of Three for each mission, replacing the previous system of ruling families, although Kulan ships in their fleets were generally still the property of specific families, forcing the flagship to retain control of all weapons in the fleet to prevent possible betrayal.
When carrying out invasions, the Kulan generally began by dispatching an evaluation team, including military and economic class representatives, to assess whether the planet should be invaded and making their decision based on the team’s final report, troops being kept in cryogenic suspension until they were ready to invade. Unlike most aliens infiltrators, who generally learn the language without working on more subtle details, the Kulan had learned colloquialisms and mimicked body language during their time on Earth, although it was implied that this might have been aided by the fact that humans and Kulans had some prior contact; at least one human had trace elements of Kulan DNA in his system, hinting at Kulan genetics in his ancestry. During their travels, the Kulan had become aware of the Daleks and the Sontaran/Rutan war, having recently lost their original Council of Three during an attack on a Chelonian planet, and had heard legends of the Martian empire, although there is no evidence that they had directly encountered the Ice Warriors; it was implied that they even knew of The Doctor, albeit mainly by reputation.
A Kulan evaluation team eventually came to Earth in 1998, crash-landing in Norway, where the team eventually split up. With the Kulan divided between those who wanted to go through with the invasion of Earth and those who preferred to leave the humans in peace, both sides went their separate ways to pursue their own means of returning to the fleet first. Contacting billionaires Arthur Tyler III and Pierre-Yves Dudoin – former friends now competing against each other to be the first privately-funded man in space after Dudoin’s wife Christine divorced him due to his lack of focus on their family , each group volunteered their technology to help the man complete his spaceship first, although Tyler was the only one who knew the Kulan’s real motives as he was working with the faction who wanted to prevent the invasion while Dudoin was simply their patsy.
The Kulan continued working undercover on Earth for the next three years, until one of their team, Menhira, was killed in Brussels by two assassins while carrying a strange package, British tourists Anji Kapoor and Dave Young witnessing the attack and Dave realising that the victim had two hearts while attempting CPR. Witnessing the report about the attack on the news, and noting the reference to the victim having two hearts, Fitz Kreiner – who had just been left on Earth by Compassion after the destruction of Gallifrey (“The Ancestor Cell”) to meet up with The Doctor after his century of exile on Earth, decided to check out the report just in case the victim was The Doctor, but he decided to remain and investigate even after the news of the victim’s purple blood confirmed that he wasn’t The Doctor. Unfortunately, their investigation went wrong when Dave was captured while trying to return the package that the dead man had given him to the people on the phone number written on the side – specifically Tyler’s team , forcing Fitz to take Anji with him to his meeting with The Doctor, his friend still suffering from amnesia and the TARDIS yet to repair the link to the interior dimensions, even if it now looked like a police box once again.
Despite the lack of a TARDIS or his actual memory of Fitz, The Doctor nevertheless quickly agreed to help Anji rescue Dave, he and Anji making contact with Tyler while Fitz returned to Belgium to try and infiltrate Dudoin’s facility and learn how he was involved in the situation. Although The Doctor was able to quickly establish the truth about Tyler’s mission after saving him from a computer virus that had been planted in Tyler’s equipment – although Tyler’s prototype Planet Hopper was damaged , Fitz was tricked into aiding Fisher, an agent of Control – the mysterious head of the CIA who had caused trouble for The Doctor and UNIT in the past (“The Devil Goblins From Neptune” and “The King of Terror”) – in infiltrating Duboin’s company and learning about the dual Kulan factions present, Duboin working with Fray’kon and blind to his alien ‘ally’s’ true goal of mounting an invasion where Tyler’s allies merely wanted to leave Earth alone.
When Fisher was killed by Fray’kon’s men, Fitz was left with Sa’Mota – one of the Kulan sympathetic to Earth – to try and escape, unaware that they were being tracked by Control’s men as well. Although The Doctor and Tyler were able to infiltrate Dudoin’s base, they were only able to stop him launching his Star Dart by using the Kulan virus they’d used against Tyler’s ship – The Doctor having transferred it to a CD in the hope of studying it later , leaving The Doctor subdued at their failure even if they managed to rescue Fitz and Sa’Mota. Returning to Tyler’s facility, the group prepared to launch the Planet Hopper to make contact with the Kulan fleet, but Fray’kon managed to break into the Planet Hopper by taking advantage of a distraction caused by Control’s attempts to capture the aliens – Control as ever relying on brute force rather than the less direct tactics of The Doctor’s allies in UNIT , Fray’kon killing Dave and Sa’Mota before taking Tyler and Fitz hostage as he left the planet, intending to claim that humanity had killed the rest of the team and should be wiped out.
Although all seemed to be lost, The Doctor and Anji found just what they needed in The Doctor’s office back at the St. Louis’, as the TARDIS finally completed its century of regeneration and the interior dimensions were restored, allowing them to take the TARDIS up to the Kulan fleet. Unfortunately, despite The Doctor and Tyler’s efforts to argue for humanity’s right to be left alone against Fray’kon’s claims that they were animals who should be eradicated – Fray’kon having already had the Planet Hopper destroyed to ensure that nobody could analyse it and find evidence that he had killed Sa’Mota , the possibility of peace ended when Anji, trying to provoke the Kulan into retreating by firing one of the flagship’s missiles after discovering their weapon control room, accidentally launched the ship’s entire arsenal, triggering an inter-fleet battle that annihilated the whole Kulan fleet thanks to the flagship’s control of the other ships’ weapons. The Doctor, Fitz and Anji only just managed to retreat to the TARDIS while Tyler sacrificed himself to stop Fray’kon (Although he admitted that he was dying of a brain tumour anyway; getting into space had been his last goal before dying), leaving the TARDIS crew to mourn their inability to find a peaceful resolution to the crisis even as The Doctor was grateful to have his ship and identity back (Although his memory would apparently remain lost until his next incarnation (“The Gallifrey Chronicles” and “Rose”).