1st edition demons were scarier

Maybe it's just me, but the demons as presented in 1st edition were the scariest. Heck, a number of mid to high level spells were all about summoning and controlling them. Maybe it was just the artwork, or Gary's writing, but it seemed more dangerous than the editions that followed.

2e really did drop the ball by renaming everything, and 3e was just too numbers-heavy to give any feeling of dread. 4e was a joke, and I still haven't picked up 5e (so maybe 5e finally fixed them). In any case, I loved the whole set-up and feeling of danger created by the writing in the 1e books.

Also, the Demons boxed sets made my Mayfair Games were fantastic. I have both, and if you ever have a chance to grab them, do yourself a favor and do it. Not only do they add tons of cool demons, there are great examples of investigators going crazy, etc.

Demon city

I recently rewatched the anime Demon City Shinjuku. It gave me an idea. Have the biggest city in your setting have a demon gate open in it. The demons take over part of the city, turning it into a literal hell on earth.

For a fantasy city, I'd think the local mages find some way to use the walls around that particular neighborhood to contain the demon outbreak. The demons can't get out, but entering the area is a death sentence.

Maybe the local government uses this as a way to execute criminals. Maybe heroes come from everywhere and attempt to seal the gate. Sneaky demons may actually get over the walls and corrupt the rest of the city. The sorcerer who initially opened the gate may be dead, or he may have become incredibly powerful, but with his death, the gate might close.

The paradox of belief in AD&D

One of the things I loved about 2e (and especially Planescape) was that the gods gained more power if they had more believers. This does present an interesting paradox, though.

If a good priest is trying to get his congregation riled up to fight the forces of a demon, he has to convince them that the demon is powerful enough to be a threat. While this certainly works to get his followers ready to fight, they have to believe the demon is powerful or they won't bother. Therefor, they are granting the demon more power, because they believe in him.

I just think this is kind of funny, but pretty awesome, as well.

Demons and Devils as Gods

This is one of the few things I believe 4e got right. I love the idea of using Asmodeus and Orcus as gods in the world. It makes them seem much for powerful and influential, which is a good thing.

Before, there was this heirarchy that demons and devils were really dangerous and evil, but still not quite as powerful as the various gods. So in a way, just not as scary. Making them gods levels the playing field, because it makes the players realize they just aren't going to be able to finally and definitively destroy Asmodeus and Orcus, no matter how powerful they get, unless they themselves achieve godhood. Even then it would be really hard for them to defeat the two.

In any world I run, gods are pretty much unkillable, just like they were presented in Planescape. It makes a heck of a lot more sense to me than the 1e version, where any high level group can go god-hunting if it wants to. Granting this ability to the lords of the Abyss and the Nine Hells seems like common sense to me.

This also makes the formation of cults make more sense, as the bad guys will actually be granted spells by their demon patrons. Before, they had to worship a different god, and also follow their demon of choice. This fixes that issue.