I considered calling this "Why You Should Never Accept Assignments From Grinning Superiors," but I'm pretty sure the higher-ups would axe that almost immediately. Got to retain the professional tone, and all. But I've never found professional tone to do anything to keep me alive on all these assignments they keep sending me on, so you'll just have to deal with this the way it is. If they don't like it, they can go there themselves and write their own guide.
Anyway, if you're reading this then you're probably doing some sort of research project or planning a holiday. If it's the second, stop now. You do not want to vacation in these places. Trust me. If it's the former, though, and you've looked at the IPC, you can probably imagine my surprise at noticing the 1 in it (IPC is the InterPlanar Codex, for you vacationers still reading), and the relatively low indexes following. Anything that central to the planar core should have been mapped out centuries ago, right?
Wrong. I did a little research, and it turns out that 953 is the CWAL sub-Net cluster. I'd heard of it, but so far managed to dodge the laser of being sent there. That place spawns subplanes faster than rabbits on prozac, and it's an anthropologist's nightmare keeping track of them. When a realm can apply to become the Elemental Plane of Duct Tape, you know something's wrong.
But back to the report, and now down to the serious stuff.
The High Heavens and Burning Hells fall under the belief-extension class of subplanes, and as such have planar alignment properties. For this compendium, I will be using the Maggottonian Pentagram and the Diendi Compass Rose to show alignment. For those of you not familiar with the systems, they are shown below:
Using these two systems, the High Heavens represent Fanatic/Lawful Good, while the Burning Hells are Selfish/Semi-Chaotic Evil. For the most part I will be referring to their alignments using the Diendi system, but the addition of the Maggottonian alignments helps one to get a clearer picture of how the realms act. It also keeps me in good standing with the Maggottonians, who would probably be slightly miffed if I did not use theirs. For those of you who do not know them, a slightly miffed Maggottonian can do more damage than an insane mega-evil warlord, and I happen to like my home world in one piece, thank you very much.
Due to the very low level of intra- and inter-planar travel from the anchor world, both realms have a relatively low range of influence. Their peak is centered on the anchor world ("Earth"), of course, and the strength drops off according to the inverse-cube rule. Though it technically extends indefinitely across the entire plane, for all intents and purposes it can be said to drop to nothing approximately 0.17 local light-years away from the planet. Until and unless the locals start traveling more, it's going to stay that way.
The Sin War
As could be expected for two planes on opposite sides of alignment diagrams, the High Heavens and Burning Hells don't exactly like each other. In fact, they hate each other, which is akin to saying a G2 star is mildly warm. Both sides will do pretty much anything and everything to turn the local humans to their alignment (one of the disadvantages of having sentience-containing subplanes. I much prefer the non-sentient varieties. They never try to meddle). Through however long they have existed, they have fought each other in what has come to be known as the "Sin War." For the most part they do it by manipulating human lives and ideologies (after all, if you remove an ideology from an anchor world completely, the plane representing that ideology disappears). Occasionally, though, they get into direct conflicts. The Hells are the ones more wont to start them, though sometimes the High Heavens will too.
An apparently recent development in the Sin War is the emergence of two "Heroes," one for each side. Apparently they were formed by sticking a demon with the evil half of a humanish soul and an angel with the good half. Why this should create some sort of catastrophe in terms of the war, I have no idea, but both sides seem to believe it totally, and belief that strong tends to create self-fulfilling prophesies. For you vacationers still reading, if you happen to be in the local cluster when the war breaks, I suggest you get out quickly. The results would not be pretty.
Now, for the specifics of the realms: