Luj

Prince Luj was the leader of the Frovians of planet Okul, a time-travelling species acknowledged by Gallifrey.

Although earlier generations of Frovians had traditionally been warmongering, Luj broke with tradition by presenting himself as a noble and peaceful ruler who wanted to promote scientific advancement. He befriended the Doctor and met him in two different incarnations, with the Doctor telling him about regeneration.

However, it eventually surfaced, to the Seventh Doctor's horror, that Luj was actually just as much of a "bloothirsty butcher" as his predecessors, and had merely been playing a years-long long con to get the Time Lords and the inhabitants of the Kollian Dimension to agree to opening up easy travel between the latter and the normal universe — with the goal of then conquering and pillaging the defenceless Kollian Dimension.

Realising his motives, the Kollian diplomat Ux hired the assassin Kasgi to replace the Doctor at the diplomatic meeting where the treaty was to be signed, with orders to assassinate Luj before he added his seal to the treaty. Luj was deceived by Kasgi's impersonation, but she did not actually succeed in killing him; instead, the real Doctor managed to free himself, and, discovering the plot, he publicly announced that Gallifrey was withdrawing its support for the Frovians — which sufficed to dissuade the other Kollian diplomats from signing the treaty, without a drop of blood spilled. Enraged, a powerless Luj swore to "have the Doctor's head for this" as the treaty was torn apart by the angered Kollians. (COMIC: Who's That Girl!)