Leandro

Leandro was a fire-breathing, lionlike alien who landed on Earth in the 17th century.

Biography
Trapped in England in 1651, Leandro claimed that he was stranded on Earth, his tribe had been overthrown, his world had been destroyed, and his wife had been killed. He asserted that he was the last of the Leonians and that he had escaped the fate of his people by fleeing through a portal created by an alien artefact that took the form of an amulet unique to his home planet.

His amulet missing, Leandro forged an alliance with the cynical and bored "Lady Me" to find it. He promised to take the young woman out into the universe in exchange for her help. Eventually, the presence of Leandro's amulet in 1651 grabbed the attention of the Twelfth Doctor. This reunited the Time Lord with Lady Me, whom he knew by her true name, "Ashildr."

After his amulet had been retrieved from the Fanshawe house, Leandro revealed himself to the Doctor, who discovered that in order to reach another world through the doorway the amulet would conjure, a death was required.

At Tyburn, a man named Sam Swift was to be executed. Both Ashildr and Leandro were in attendance. Ashildr used Leandro's amulet to kill Sam Swift and open a portal; this revealed an army of Leonians was alive and ready to invade Earth. His lie discovered, Leandro admitted that he had tricked Ashildr, but when the girl used a Mire medical kit she had in her possession to reverse the death of Sam Swift, the portal she had opened was closed. For failing in his mission to keep the portal open so his people could invade, Leandro was killed. (TV: The Woman Who Lived)