Hey guys, Last night I just ran a successful session that involved 25 Plus units on a board that couldn't fit all of them. Not bragging or anything, but I think this idea of large combat can be easily mishandled and difficult for DM's at times. So here's a NOT short list of tips to help someone if they have this cool idea of a big battle sequence but can't exactly imagine how to make it work smoothly. This is a long one, so if you want a good read sit tight.

I'll cover:

Keeping track of hp, initiatives, what abilities, how to make these encounters special, and other personal things.

1. Initiatives

breaking this down should be the first step, you'll see a lot of generalizations too. Just take the highest initiative (Or lowest) bonus this large army would have, and just use that. Put that large group on the same turn. This will help combat run very smoothly, and when it's the baddies turns it will feel more intense sense they'll all mobilize at the same time. It may be bursty, but it also allow players to adjust to battle tactics.

2. HP

Don't keep track of every single unit's HP. You will bog down your brain power for the session, and time with the book keeping. Instead, let the players work with you on this one, use general numbers. Remember, monsters can have a range of hp. Usually working with low numbers will help out a lot. So if you don't want your monsters to get immediately blown away, just hike up the ac, or if you have a fireball sorcerer with fire affinity, hike up the dex or give them fire resist. It's a lot easier than throwing hp more hp on them.

3. Abilities

Mon's that have abilities should use tactics that surround these. A goblin army will usually try to overwhelm opponents while slipping away and hiding, and if the party isn't prepared it's a big problem for them. Something like bearded devils for instance would have someone able to cast 'Darkness' in an area to give their opponents disadvantage while not effecting their own armies. Also helps out with the fireball wizard or sorcerer from making the encounter a joke.

This will probably help you come up with good ideas for some really bad monsters in the MM that don't really seem interesting, but in mass are a problem. Lemure's would be a good thing to use and can be backed up by the stronger bearded devil I mentioned before. Especially since that fireball problem is now resolved (Lemure's are immune to fire)

4. Specialization

Now that you have this idea for an army, why would the players fight this army? Will they have time to prepare? Can they hire more people to come help? What is the point of defeating this army? Do they have something or trying to keep something safe? This should be a pretty big event and allow the players some extra agency makes them feel engaged especially if they are the 'power gamers'. Adding story to it is a major plot point to me, because if you're going to do all of this work, sit down, and do an encounter that takes up almost the whole session. It should be worth it to the players and as the DM reward them for this. Either it be some sort of opportunity to meet a king, find where the BBEG is, or even something that helps them with their big fight against said BBEG.

If this doesn't progress the story, and the players don't gain anything, they'll probably feel like "Wow, what a waste of time" if you are using milestones for fifth edition D&D leveling. Make this an occasion, a part of the campaign to remember and love. Everyone will forget it if it was for nothing.

5. Officers

Every army has some type of commander or officer hierarchy. Goblins have a simple hierarchy, and have simple tactics as a result. Fiends have a great structure for this as well, and have even more strengths to use for combat. These officers should be special and should be the 'main target' Most warfare breaks down if there is no one commanding or in charge, so let's make that happen.

Less so with fiends since that opens up an opportunity for sweet promotion in the nine hells. If there is a paladin, and holy water is just flying everywhere, they'll try to regroup and fight another day so they don't permanently die. Goblins, will run in fear since survival is their main goal. This is why this is after 'specialization'. The type of army, their goals, and lore. It all manifests in this, how they perform warfare tells the players about the world, how these creatures defeat their opponents.

6. Why as a DM should I do this?

It is completely up to you, and it's a tool you can use if you've had a long gap for a challenging fight, or have had so much RP that your players just want to murderhobo something. This scratches an itch some players have and should sate their want for combat for a while. On top of this, what you can do is force the player to use resources. If your players have been going nova, defeating every encounter in front of them, put a bigger challenge after that. Be it a 'Boss Monster', a social encounter to help lull them out of combat mode, or set up a nice big cliffhanger to leave your party to stew over a full week or fortnight, or whatever. Use this opportunity to bring a little more tension, and then, rest.

After this, giving the players more story is nice. Don't overwhelm them with a bunch of encounters (Ironic I know) or the players might ask you 'What are we trying to accomplish again' if it all blurs together too much. Let them rest their brain power after that battle, and especially yours if you're the DM.

7. Caution

This can EASILY go wrong. Take Caution

Some horror stories may circle around this. Only do this if you're sure it's what your party wants, otherwise your planning for this even might be for not. If this is something your party should dread out of character, try to do something else. If you're a newer DM, this sounds really cool and that you should try it, don't.

Not yet at least.

I seldom don't recommend certain things. If you're newer you're pretty prone to some mistakes, please don't. As a result this three hour session could turn into a two week encounter. My players we're pretty afraid because I myself have DM'd for only 2 years. I used goblins and worgs because they we're easy, and you can play off mistakes as 'goblin's are dumb' but fiends, they don't make mistakes. They literally fight all. The. Time. Their existence is constant war, so mistakes should be less likely.

More importantly, if you are willing to take this risk and heed my warning, and STILL go on with this. Prepare for consequence of a bad session or even a slog, Eww no one is having fun.

Now the MOST importantly, ask for feedback. I can't stress this enough. In order for you to be better as a DM and conduct a better mass combat session, ask your players what they thought about it, If they should try it again, or refrain from it in the future.

If you're really in this situation where no one is having fun, don't be afraid to press the emergency "DUES EX MACHINA" button. Get them out of there, tell them that you wanted to try something different. As the DM you're still the curator of fun, and if it's not fun, don't bother. Maybe this set back triggers other story things that have to be done? Maybe all they had to do was just see the army? Don't be afraid to improv. It's your best tool for when it all goes wrong.

Anyways, thank you for reading this long list. Please leave feedback below, and for those about to rock, we salute you.