The Grand Serpent

His Supremacy the Grand Serpent was a political figure on Inston-Vee Vinder's home planet. True to his name, he had the ability to project serpent-like creatures out of his body before reabsorbing them, being part of a rare binary demi-species. He interfered with UNIT using the name Prentis.

The Grand Serpent confirmed to the Thirteenth Doctor that "the Grand Serpent" was not his birth name, but rather a title he had earned, many years prior to their meeting. (TV: The Vanquishers)

Biography
The Grand Serpent met the Alforia to discuss terms. Once the official meeting was concluded, he ordered Vinder to cease recording and then demanded the Alforia hand over five dissidents being sheltered in their territory to face trial, and for another four, all relatives of his critic Frey Sampor, to suffer a fatal accident. Inston-Vee Vinder reported the incident, resulting in him being reassigned to Observation Outpost Rose. (TV: Once, Upon Time)

He positioned himself on Earth in 1958 in order to assist the founding of a new organisation known as UNIT. In 1967, after being identified as an alien by General Farquhar, he began a streak of assassinating those who stood in his way. In 2017, he encountered Kate Stewart, informing her that UNIT funding was being cut. When she retaliated by threatening to expose his history with the organisation, he attempted to kill her by leaving a bomb in her house. Later, he ordered UNIT to prepare missile strikes against various Earth cities before informing the Sontarans, with whom he had struck a deal, that everything was ready for their invasion of Earth. (TV: Survivors of the Flux)