Mephistopheles Arkadian

Mephistopheles Arkadian was a human arms dealer who also dealt in temporal artefacts. He was in league with the Free Time movement, but stayed impartial. Leela, K9 and Torvald encountered him on Gryben whilst searching for about the movement and the threat of a Timonic Fusion Device. He led them to Nepenthe and was himself was taken to Gallifrey. He was the first person to hail President Romana as 'Imperiatrix'. (BFG: Weapon of Choice)

Later he invited Romana and Leela to the Calais Transcontinental Express to learn something about Miss Cecelia Pollard and Commander Torvald (BFG: A Blind Eye)

After the fall of the Matrix, President Mathias invited him to remove Pandora's stockpile of weapons. Mathias, however, was in league with Irving Braxiatel, to whom he had sold his Collection. When Braxiatel's plan was completed, he took the battle TARDIS to bring the weapons, but was killed by Elbon, who was affected by the Dogma Virus. (BFG: Panacea)