Priscilla

The Spider Queen is a champion which hasn't been released, and the skin is in the game files.

It's rumored that Spider Queen was reworked into, since that was the name used for Spider Queen. Also in early development Nidalee used poison in all of her attacks and her Prowl caused her to be camouflaged.

She may be based upon the DotA hero "Broodmother" seeing as they are both spiders.

However, on May 22nd 2010, Coronach (Associate Game Designer) stated: "To fuel more speculation, is not Averdrian and Nidalee is not the Spider Queen."

On August 19, a sneak preview of was released. While the two share a similar appearance (Both having arachnid-like legs, the design of which are near identical between the two Champions), it is uncertain as to whether their skills would have shared similarities due to a lack of information on The Spider Queen. It is possible that she has been reworked into Urgot, but this has not been confirmed. 

Abilities
Images and names extracted from the game files.