Domain Play Starts When Players Start Caring

A Castle is Just a Big Stone House

Domain play in D&D often seems tied to when the game gives you permission to build a castle. But you can just do that. The game cannot stop you from figuring out how much gold it costs to build something. If you care, if you want to do it, do it. Talk to your referee and make it happen. It can be a cool clubhouse or the center of the game. 

Politics is Just That Guy Over There

If you've ever worked with factions in a game or had someone with power over the players tell them to do something congratulations. That's political gameplay. Sure the machinations may be more on the "How do we fireball this guy?" than the clever maneuvering and manipulation of public opinion but it's still politicking.

Translate your factions in a dungeon into factions in the world. Those guys over there? Basically goblin in their methods and actions. Those other guys? Wouldn't you know it, basically lizardmen ideologically. Simplify and map things to what already works for you in the dungeon outside the dungeon.

There's a deeper look at this where you convert a dungeon into a domain scenario, but we don't have time. This is a short post, don't you know?

War is Just Guys in a Field

Standardize soldiers based on what they can afford. These guys all have leather, a shield and a spear. Those guys all have chain mail and crossbows. Great. They are rolling with +0 and have buckets of d20s. Don't bother with HP. Hits down a soldier. Morale check when an officer dies and at half hp. Good tactics determine initiative. 

This works fine at small scales too. It's swingy, sure, but your goal here is to give folks a fast way to resolve large combats, not play a balanced and finely tuned wargame.

A Spell for Domain Play

Several of the spells carried forward in early editions of D&D clearly emerge directly from the wargaming background of the game. Hallucinatory Terrain being a key example. The number of targets some spells effect lines up more with small unit combat than it does four jagoffs in a dark tunnel. Here's another one of that kind.

Crawling Mire (2nd Level Magic-User Spells)

Affects (30"x30" or 33" diameter, duration: 1-6 turns + 1 turn/level, range: 12") 

Causes the ground within the area to become muddy and foul underfoot, requiring careful movement from man-types and giving them -2 on their initiative if rolling. It returns to good footing at the end of the duration.