An alien being from the planet of the same name. Sleeches are primitive, parasitic creatures that feed on other creatures for their sustenance.
A Chaos Stone landed on the planet Sleech and caused the primitive, amoeba-like brain of a Sleech creature to transform, and evolve into an intellect. The Sleech fed on the life of the Chaos Stone while the Chaos Stone amplified its negative energy from the life of the Sleech. This Sleech was collected unknowingly, from its planet along with the Chaos Stone, by the slave-trader and poacher, Vagus and placed in the zoo in Astra’s tardis. The Sleech managed to exit the tardis on Earth in the 1920’s, and there, under the influence of the Chaos Stone, began to create a ring of energy which negatively influenced the Secret Brotherhood of Bully Boys; prompting them to commit mischief in the city of New York. The energy created by unity, goodwill and positive vibrations, create a barrier to the effects of the Chaos Stone and act as a poison to the Sleech, causing it to shrivel up and die.