The Bend of Time allows one to access places that do not exist and are not Entity-defined eras, however, leading me to believe it is simply a game device without explanation.
"...simply a game device without explanation."? Putting aside the fact that I agree, that kind of goes against the spirit of this site. Shame on you, my almighty overlord.
I personally would explain it as the dimensional equivalent of The End of Time. Where TEoT is the point of least resistance on the timeline, TBoT is the point of least resistance between different dimensions. It has certain parallels to TEoT: You can access it from either dimension (although you can't travel to the other), it has portals to different places (rather than different times), not to mention the similar architecture.
The portals might be connected to the memories of the travelers, allowing them to relive (in a sense) past conflicts. Ozzie, Slash, and Flea, on the other hand, wouldn't have a portal as they hadn't previously been encountered. "Why them?" is extremely hard to answer in game terms. Possibly the octopus (or Gaspar, or whoever) has some manner of control there and brought them there on a whim.