Sponge is a Warpie and is either a child or has the mind of a small child. This has never been clarified. However, she was collected by the forces of the R.C.X. for both her own safety and the safety of the British people.
Sponge later was assigned as an escort to Cerise while Excalibur was being held at Cloud Nine by Peter. 
Presumably Sponge eventually lost her powers, as did the other Warpies.
Currently none, all of the Warpies were depowered by Captain Britain on Otherworld using the Sword of Might.