Without going into too much detail, I'm looking for help or examples for writing a 5th edition adventure / small-scale sandbox that will put the players in the role of defending a small village from a hostile lord. I'm hoping for a variety of encounters with both combat in the village and some exploration and perhaps a visit to a nearby "dungeon."
Any general pointers? Any similar adventures written for any edition of D&D that cover this sort of ground and I could draw inspiration from?
Some defense-oriented D&D adventures available in print &/or online:
Note: the Seven Samurai were veteran warriors (mostly), so you may want the PCs to gain some levels (and HP) before reaching your huge invasion scene (if any).
See also a previous discussion.
I don't know about existing adventures, but this is one of my all time favorite films and I've considered running a game like this myself.
As is always my advice, begin by figuring out what will happen if the PCs do not come to the farmers aid. I'd expect it to go down like this:
The Bandit Leader wants to continue bleeding the farmers dry, leaving them with just enough food to live through the winter, but all else going to the bandits.
The Farmer Elders know they do not have enough food to survive the winter and have failed to hire any help, they really have no choice but to try to fight anyway. They have no skill in this so they are likely to do what is obvious: let the bandits come collect their tribute and attack them with farm equipment.
They might succeed in this initial fight, but it will draw the attention of the Bandit Leader for a counterattack. The Leader will send in scouts and spies to see what (if anything) the farmers are planning.
I think the Farmer Elders are smart enough to know that beating back the small group of bandits won't be the end of it. They'll probably set up some basic watch groups at the logical entry ways to the village and when they spot an attack they'll raise an alert and they will fight in a barbaric fashion in small groups very ineffectively.
The Bandit Leader will lose probably 1 man for every 10 farmers killed and will probably order his bandits to try to disarm and capture as many farmers as possible and re-enslave them to keep working the farms for them.
The Farmers have almost no way to pay the PCs. They will try, and let the PCs feast, but you should make it clear to them that while they are feasting the Farmers are eating scraps. Assuming your PCs are good, they should be willing to protect the Farmers for free (maybe for whatever the bandits carry) after that, seeing how miserable the Farmers really are.
From here, you need to be really flexible. Try to describe potential. Draw a map with obvious entry-ways and also less obvious ones (over the fields) and natural defenses like rivers and mountains. Describe what the Farmers have at hand (bamboo, farming sickles, rope, so on) and let the player's be creative with those items. Maybe they'll think to sharpen bamboo as pikes/spears or for making barriers. Maybe they'll think to dig ditches to trip horses in the fields.
Maybe the PCs deal with the scouts and spies. If they don't think about that possibility, nullify some of their traps with phrases like "The horsemen weave their way past each covered ditch, as if they already know the ditches are there" and have an NPC spy they trust try to backstab them.
If the PCs do a good job, they should be able to save many of the lives of the farmers and end many of the lives of the bandits and they should be able to hunt down and confront the Bandit Leader in his own camp.
In the starter set is a decent setup with chapter two for the bandit gang that works in the city. It can be adapted, and the information in it can be used somewhat loosely for how a hostile lord might try to take control of a small town. The free printed materials for support of Tyranny of Dragons can be useful as an extended monster manual that includes details on things such as knights, guards, and commoners, and would therefore help produce quality encounters as well. A small amount of alteration to the knights to make them closer to dual-wielders would fit thematically if you truly want a more samurai feel. Both of these resources carry enough information to build encounters, and...
Small spoiler:
The starter set actually has a decent set up of the city that is besieged by, in this case, a bandit-gang looking to extort money from the town. They are being hired by an outside entity as well, and that can be a useful tactic to a rival lord trying to take control.
This is more to help you build your own, since your ideas are so specific. Samurai would translate in to 5th edition as either a med-heavy armored dual-wielding fighter, or a dual-wielding paladin (with an appropriate oath for the particular ideals of that Daimyo and Samurai). NPC's using the feats specific for dual-wielding will certainly be even more authentic, as it would allow someone to use larger swords while dual-wielding.
Some additional ideas:
