Warhammer 40,000: Chaos Gate

Chaos Gate is the greatest* computer game ever.

*"Greatest" assuming you're into really buggy, immersion-driven RPGesque X-Com'ish turn-based grimdark scifi games, that are really buggy. Did I mention bugs?

Short synopsis

Forces of Ultramarines under command of Captain Kruger fight against forces of Word Bearers under command of Chaos Lord Zymran. Both forces want to take control over Pre-Heresy relic called the Concordat Chaosium. And to kill each other.

The game was made when Warhammer 40,000 was still in 2nd Edition, so many things are quite different, mainly weapons and psychic powers.