THE BORDER BETWEEN TWO ELEMENTAL PLANES IS RIPE FOR EXPLOITATION BY INTERLOPERS

Elemental planes are boring because the environment is so extreme the PCs will have a hard time adventuring there. More interesting, as stated by others, is the border between two planes. Take FIRE & WATER.

The borderland would be STEAM and maybe as this elemental conflict rages a third party, dwarves, move in to build a city based on steam-powered everything. The elementals too embroiled in their own conflict are now slaves in these objects, structures, and mechanism.

And to add on top of this, since the planes have proximity based on belief and not actual distance, maybe this City of Steam is in conflict with The City of Brass. So even though they are planes apart it is easy to find gates from one to the other because they are believed rivals. Sorta like if New York and LA were as far away from each other as an inverse of their animosity toward each other.

So there are two policial factions in The City of Steam: The NEAR which believe an attack from The City of Brass is imminent and the FAR which seeks to eliminate knowledge about The City of Brass and deny its existence to keep it away (out of sight, out of mind).

PUNNETT SQUARE OF CREATURE COMBAT

Influenced by Darkest Dungeon & Into The Breach, here is a way to remind myself to mix in melee and ranged units with intelligent antagonists. I think there are really four basic components: Melee, Ranged, Damage, Effect. This gives four combinations:
Melee X Damage; Ranged X Damage; Melee X Effect; Ranged X Effect.

Thinking of the Beastmen in my Thracia campaign and keeping it simple:
Ax-1d6 dmg; Bow-1d6 dmg; Ram!-Push 1d4 x 5'; Caustic Spit- 1 dmg; blinded 1d4 rounds.

DUNGEON DESIGN #1

Arnold K from Goblin Punch has a nice list of things to include in a dungeon. Something to...

1. steal; 
2. be killed; 
3. kill the PCs; 
4. chose between; 
5. talk to;
6. experiment with;

BACKGROUNDS IN CARCOSA

Great post from Hmmm Marquis on backgrounds, starting equipment, and goals for characters in a wasteland, Carcosa, Black Sun, or Synthexia campaign/hexcrawl. I might be tempted to change the d20 to a d30 table and add more overtly strange techno-stuff to make it more Carcosian.

ALTERNATIVE CLERIC

I play a mostly B/X or LotFP flavored D&D which leaves little room for cleric diversity. Ideally, you'd want to have an individual spell list for each deity, but that can involve almost too much prep work depending on how big the pantheon is (which has posed a problem for my Yoon-Suin campaign). Here is my fix:

• Turn Undead becomes "Turn the Unholy".  Define what "unholy" is for the cleric. If it is as frequent as undead, keep it to one thing. If it rarer, maybe make it 2-3 things.
• Steal Lay on Hands from the Paladin and have the cleric do something thematically similar once per day. Pick a level 1 spell and add PC level to any number. The cleric class is basically a paladin anyway.
• Favored Weapon- cleric gets one, but disadvantage or -2 to-hit with anything else.
• Reduce spell list to only gaining 1 spell per level, it has to be thematic, and each spell, or miracle, can only be performed once per day.

A LOAD OF ENCUMBRANCE RULES

Goblin Punch using Triple X Depletion rules. Anti-Hammerspace rules from Matt Rundle has good appeal due to simplicity as does using STR/CON as the number of "slots". Currently, I use LotFP's 5 slots equals 1 encumbrance point method.

CARCOSA IS BETTER WITHOUT LOVECRAFT

D&D has its own set of strange creatures that could function as good substitutes as any Lovecraftian horror they are inspired by and, when placed together, offer an equally strange, dangerous, and morally questionable environment for the humans to move around in.

• Neogi (as a substitute for the mi-go)
• Mind Flayers (substitute for the Primordial Ones)
• Grill & Grick (as a unified hive species or mi-go substitute)
• Slaad (substitute for Deep Ones)
• Gith (substitute for Space Aliens)

CARCOSA IS PEOPLE

It wasn't until I made a Hex Kit map of Carcosa that I realized just how many human settlements there are. There are also two human "cities" (hex 0313 & 2113). I think three things help a DM maximize this: (1) the encounter reaction roll; (2) Chaotic, Neutral, & Lawful alignments; (3) PCs natural tendencies to ascribe all sorts of weight to Carcosa's non-mechanical color system. A key question for the PCs in a Carcosa campaign: "What are you going to do with all these people?"