Frankly, we're not exactly sure what Stealer is yet. But that's okay, because neither is its developer. Looking very much like a 16-bit Mass Effect with shades of Ghost in the Shell and Flashback, Stealer's trailer is one of the most impressive promos that have arrived this year, not least because of a blistering soundtrack and the kind of direction that makes it feel as much music video as video game advert.
One problem though. There's every chance that the game doesn't actually exist at the moment. Developer Winged Doom has admitted that the trailer is a mock-up for a game that he's still "groping in the dark" to define. Frustrating, but not much different to what triple-A publishers do with CG 'reveal' trailers all the time. WD is talking in terms of a heavy emphasis on atmosphere and exploration though, and references both Metroid and block-pushing puzzler Sokoban as influences.
You can track the progress of the game at Stealer's ModDB page. And it looks like that'll be something worth doing, if only for the hope of more extracts of that soundtrack.