HIVE

Why?

Is it because the Protoss are partly inspired by Byzantium?

Are they? :O! I didn't know! What parts exactly?

But in answer to your first question, it's just because I like history in general... though I should confess I don't read all that much, and I kinda wasted my school years attending History lectures with indifference =(

Some of the unit names, like Archon, which was a Byzantine title. I guess not that many lol. I would need to replay the games or read up on some lore to refresh my memory and see if there's anything else.

Or even before :D
https://en.wikipedia.org/wiki/Archon

But honestly the protoss are a syncretism: Egyptian, Persian, Greek, yeah.

Yeah. Caste system like in India + elements of Vedic cosmology in their belief system, Zealots like the ancient Jewish warrior sect, the Khala = collectivism, Dark Templar = individualism, etc. I wonder if everything was intended or they just threw in whatever they thought was "cool" without giving it much thought. Much of it was further developed via books and the sequels.

Much of it/the background lies in the manual:
ftp.blizzard.com/pub/misc/StarCraft.PDF