Re: Mythological source of Tartarian Gate
Tartarus is the deepest section of Hell in classic Greek mythology. It's where most of the worst offenders (primarily the ones that REALLY angered Zeus) were imprisoned. This is where the Titans were imprisoned by Zeus after he overthrew Cronus. Cyclopses were also imprisoned here by Uranus, so it's not surprising those are the two most common results from Tartarian Gate.
Tartarus was surrounded by a huge bronze wall and was forever in the darkest of night with no light at all. The sole gate into Tartarus is guarded by the Hecatoncheires, huge beings with 50 heads and 100 arms. There were three: Briarius (also known as Aegaeon), Cottus, and Gyges (Gyes).
NOTE: I knew that Tartarian Gate referenced Greek myth, but Google is where I got 90% of that information
A quick search can do wonders.