D&D 5E How to handle massive oncoming swarms

[aco175]

I like what @Shiroiken said about a huge statblock for the mob. Say it was a huge creature with 16 squares, I would have roughly 32 monsters in it and a total of HP that ! can track for half and quarter HP. When the mob reaches half HP if shrinks to only a 3x3 square mob and at 1/4HP, it shrinks to 2x2 tiles. I would give it enough HP and attack power to make attacks worthwhile and some lair actions where it can move, break in half, and attack on others turns to try and keep it fun. I would plan to regenerate it with new monsters joining each round. Say the mob was knocked down to 1/4 HP and became a 2x2 mob and them 10 more monsters joined, it would become a 3x3 and gain 50HP or such.

 

[JiffyPopTart]

My solution:

Define the area that the PCs have to "obtain the MacGuffin" and exit. Have the area begin with clear terrain. As the hoarde approaches from the water it is represented by a moving block of difficult terrain, each space of which is going to "attack" any character that ends their turn next to it. While most of the attack would be directed at melee range, you still might want to have some "ranged" attacks from the terrain for characters not in the scrum.

Come up with a fair mechanism to allow PC attacks and defensive options to negate some or all of the incoming attacks from the terrain for a round (or more depending on the solution).

This will encourage the PCs to bunch up defensively inside the hoarde (to minimize incoming damage) but also allow a character with an ingenious solution (spiderclimb or something) to still remain viably on their own.

 

[Quartz]

The proper solution is to not allow spells like Spirit Guardians in a game where hordes of zombies etc is meant to be meaningful.

I beg to differ. Tempting the PCs to use Spirit Guardians means that the PC cleric has one less 3rd level slot to use for Revivify or Dispel later on... It's no different to the guy with the machine gun: if he uses his bullets now he can't use them later. The horde invites expenditure of a meaningful resource.

 

[CapnZapp]

Because the thread was about creating swarm stats, not how to beat swarm stats.

Well, no - I read the OP as using "swarms" in the general sense, rather than a specific D&D term.

Using Swarms (with a capital S) isn't the only solution to rat or zombie swarms (with a lower-case s), and for those DMs that go with individual monsters en masse, it is essential to discuss the Spirit Guardians spell.

Best Regards,

 

[MNblockhead]

If the idea is just to get in and get out from a certain point while effectively endless hordes are swarming you, I'd probably structure it more as a chase or skill challenge, rather than a combat. Basically treat the horde as a debilitating environmental effect to be overcome.

Someone else up thread recommended treating swarms as environmental hazards. What would this look like?

 

[MNblockhead]

Well, no - I read the OP as using "swarms" in the general sense, rather than a specific D&D term.

Using Swarms (with a capital S) isn't the only solution to rat or zombie swarms (with a lower-case s), and for those DMs that go with individual monsters en masse, it is essential to discuss the Spirit Guardians spell.

Best Regards,

My initial thought was how to handle a continuing stream of mobs, but it has grown into a much cooler discussion or swarms as statblocks, hordes vs swarms, swarms as environmental hazards... lots of cool ideas I'll be using.

 

[Oofta]

If you have a truly endless stream of bad guys you have two goals.

First, you need to reinforce that simply fighting the bad guys is going to ultimately fail. The trick is how to do it without DM fiat, a boring slog or leave people with a sense of hopelessness.

So one possibility is to set up an initial encounter where they have to fight a mob. Make it a tough fight but winnable. Then let them know that this was merely the first wave and they now see wave after wave coming at them. Fighting them all is not going to be an option.

Alternative is to just throw the endless mob but give them a temporary escape/safe spot.

Next now that they realize they can't win the day through fighting head on, give them multiple options on how to redirect, bypass, nullify or push through. The tricky part is giving them enough options that they feel empowered and have options.

So yes, you can treat the mobs like a hazard/trap. Maybe a PC have to get from point A to point B to drop a drawbridge. Others can assist (ranged attacks vs enemies, illusions and so on) but one PC simply has to work their way through the mob and make strength/athletics checks with DC reduced by actions of the rest of the party, possibly with advantage if the party is clever.

So at that point I'd probably want to try to set up different scenarios with different scenes requiring different skills and solutions, or possibly multiple solutions.

In addition, of course there's always the "you failed at that part of the challenge so roll initiative to fight your way to safety".

Hmm. I may have to steal this idea.

 

[JiffyPopTart]

Someone else up thread recommended treating swarms as environmental hazards. What would this look like?

That was me, and in my minds eye it would look like a growing single "mob" of creatures that eventually fills every square in the entire room (unless your mob isn't that big, but the OP seems to indicate it would be). The only space it doesn't fill is the space taken by the PCs. In order for this to not be instant death you have to allow the PCs to move through the mob, which is why I suggest it be treated as terrain more than an actual monster on the map, however it is still areas full of fishpeople or zombies or whatever your mob is.

 

[MarkB]

Someone else up thread recommended treating swarms as environmental hazards. What would this look like?

Have it be essentially an ongoing skill challenge, except that instead of failing the challenge after a certain number of failed checks, failures result in damage being taken due to some of the attackers having gotten too close.

In this scenario, players could use attacks instead of checks, but doing so wouldn't progress the group towards their goal - it would merely reduce the DC for other checks that round by relieving the pressure on the party. Area-effect spells like Fireball or Spirit Guardians would be handled the same way, but would have a greater or longer-lasting effect. Other spells or abilities, such as movement-enhancing spells, could be used to grant advantage on checks or even grant an automatic success, at the DM's discretion.

 

[GMMichael]

Simple version:
PCs take a fixed amount of damage each round unless they make a successful roll:

• Attack, allows you or an ally to make a non-attack or non-defense on the next round.
• Defend/saving throw, if you're not skilled enough for attacking, or want to defend a weaker ally.
• Move, probably needed to get to the ending-the-swarm solution.
• Skill, used for ending the swarm auto-damage.