This game suffers from an identity crisis. It was originally to be named "Ruin: Return of the Gods", and ended up being released as "Powerslave" in the US, "Exhumed" in the UK, and "1999" in Japan.
Demo (10 Mb)
Download It! (9.41 Mb)
(please let me know if these are what they appear to be since the demo version is actually somehow larger.