This has to be a first!

[PvK]

Spartan youths were frequently raised and trained by older warriors, and part of the training, it's generally accepted, included homosexual relations. Though, they were more bisexual rather than gay - they had wives and children, too.

Dominions isn't the first computer game to have Spartans, although AFAIK it might be the first to mention it, though I doubt it - there are many games out there.

As for the first to have blood magic and crossbreed monsters... nah. I remember a game back about 1989 that had a "sacrifice virgin" command... another that had male prostitution as a way to make money for your hero... there are quite a few games that include necromancy, vampirism, abominable monsters, and so on. Spiderweb Software has its "Geneforge" series of games, which center around making mutant monsters.

PvK