Ju'wes

The  was an intelligent lizard-like reptile from the Matrua Nebula that had been at war with the Re'nar.

Biology
Both the Ju'wes and Re'nar were larger than a man when standing in a hunched bipedal position. They had long sharp teeth and claws. Their forelimbs had hands with four fingers and they walked on the two digits of their hind limbs which kept their dewclaws off the ground. Their tympanic membranes were close to the surface and they were leechers that could go without feeding for weeks. The "Sir Charles Warren" Ju'wes had a pale purple coloured skin. Mac'atyde called them a weak race which may not have been a literal statement. (COMIC: Ripper's Curse)

History
Hundreds of years after the 19th century the Ju'wes and Re'nar engaged in a war during which both sides did terrible things. The Ju'wes won the war by being willing to commit self-sacrifice. After the war most atoned but the Re'nar Mac'atyde continued to murder and was pursued by a Ju'wes who considered it his personal responsibility. Both crashed their ships after they fell through a time rift to Earth in the year 1888. The Ju'wes used a shimmer suit to take the place of Sir Charles Warren when he found out Mac'atyde was committing the Jack the Ripper murders. Mac'atyde intended to pin the blame on the Ju'wes race and left graffiti on Goulsten Street referring to "the Juwes". The police believed this referred to either the Jews or was a Freemason reference. (COMIC: Ripper's Curse)

Behind the scenes

 * The Ju'wes and Re'nar might be the same species. Skin colour is the only obvious difference between Warren and Mac'atyde and it apparently doesn't make a difference to the Doctor who had already seen Mac'atyde undisguised.