Warthur
Focusing largely on chilled-out psychedelic instrumental material, Staircase Infinities consists of off-cuts from the Up the Downstair session which were unable to be finished in time for the album's completion. In the long run, I think it's for the best because that album is pretty solid as a single album and might drag if padded out further with this material, but as a half-hour EP this isn't bad.
It reminds me of the sort of material which some of the jam-oriented space rock improvisational groups of the early Krautrock scene might have had access to with access to modern (for 1993) recording equipment; it clearly isn't totally improvised, there's enough later embellishments and samples slipped into make that unlikely in the extreme, but it does have the quality of material workshopped through such a process. A good thing to track down if you are very into the space rock side of Porcupine Tree; though the original release has vanished it has been recompiled elsewhere, such as on the expansive Delirium Years boxed set.