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5E I think I am going to stop using solo monsters.


Last night we performed a little test in my 5E campaign. The party of 8 5th level PCs had acquired a collection of magic items that ended up being cursed by a demon (a marilith) and through the item she could spy on the party and even send demonic troops to attack them. They researched ways to lift the curse and opted to use the "summon her and kick her tail (heh) and get to keep the gear" over the "remove curse and lose the items" option.

Now, they were able to specify the time and place of the encounter and prepare in advance. They set up a magic circle and a few glyphs of warding, spending 800gp in the process. They summoned her into the circle which fired off the glyphs, creating clouds of daggers, and got a surprise round on her. She was destroyed before her first action. That is a CR16 creature.

I don't think solo creatures work with 5E at all. Every time I use a boss critter, even one with lair and legendary actions, the large party just runs over them, no matter how outmatched they are by the math. The action economy just does not work at that scale.

I think, therefore, I am going to adjust my encounter philosophy: bigger, more diverse groups where the "boss" critters aren't necessarily simply tougher but are the ones capable of wrangling such groups. I am also throwing out the CR system for 5E completely: it just does not work any better than simply eyeballing it, IMO.

Anyone have different experiences?

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Magic Wordsmith
By the way, the difficulty of a Marilith versus eight 5th-level PCs is only Hard and that assume the PCs haven't set up the encounter to take her down. So that clearly reduced the difficulty from Hard to Medium or Easy.

In a "Hard" challenge, it "could go badly for the adventurers. Weaker characters might get taken out of the fight, and there's a slim chance that one or more characters might die." That is the expectation one must have when judging if the expected difficulty was in line with the actual difficulty.

Another expectation to have is that a well-designed encounter can have its difficulty adjusted by good strategy and tactics by the players. That is a sign their decisions were actually meaningful and this is what we want in our games, right?


Large number of heroes with time to choose and prepare the field of battle defeated a 'hard'(by the book) encounter?

Stunned. 5e is broken.

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The hero you deserve
Every good fight I've had in 5e has a number of monsters at least close to the number of PCs (we have 6 PCs in my main group). 1-2 monster fights get butchered, even when the monster can 1 or 2 hit a PC. Having greater numbers means a lot in 5e, because of the fairly small difference in offensive output as level increases.


I have three rules for solo encounters:

  • When I want a monster to fight solo, I beef up its hit points. 5E doesn't give PCs enough credit for being able to dish out damage. This is a problem, but it's very easily solved.
  • I don't use non-legendary monsters in solo encounters. Ever.
  • I don't allow the PCs carte blanche to prepare a deathtrap. If the monster is in its lair, then it has defenses sufficient to prevent an ambush. If forced to fight outside its lair, it takes precautions against being ambushed and annihilated. If possible, it engages the PCs at a time and place of its choosing rather than theirs.
When I follow these three rules, solo encounters work fine. The scenario you describe violates all three, and the result is what I'd expect.

(Also, as Iserith points out, it's only a Hard encounter to begin with, and encounter guidelines do not and cannot take player skill into account. What's Hard for a casual playgroup is trivial for a skilled group of optimizers. This is not the fault of the rulebooks; it's your job to know how skilled your players are and set encounter difficulty to challenge them.)
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First Post
Mariliths are also not designed to be solo monsters, so it's unsurprising that their action economy doesn't work against a two tables-worth of PCs. That said, each turn it probably would have killed at least one PC, given its seven attacks. Also, if the Marilith could spy on the PCs and couldn't prevent them from summoning her into a deathtrap, she probably deserved what she got.


How did they find out it was a Marilith and specifically know how to summon the right one?
How did they summon it?
Why didn't she know they conspiring?
Why didn't she have anything in place to hinder, protect or at least warn her of things like this?( 800gp is not a big barrier)
Where were her own magical items? Surely you gave her some if she was comfortable cursing and throwing out magical items.

8 PCs is well above what the games CR is designed for and even then it is only a Hard encounter. Which drops down to being even weaker when you consider that you handed them a surprise round with an area that was prepared for the situation.

Put simply, without boosting the Marilith or giving her a real turn in battle it is just handing a victory to the PCs.

This said, if they took precautions in every possible way and you couldn't think of anything the Marilith would do -shrugs- maybe they deserve the win. But probably better to keep from saying the system is broken in this particular case.

Heck, give monsters the Alert feat if you are worried, it helps. But they are a group of 8, they do need more thought put into the encounter tactics from the other side because of it.


If the Marilith was spying on them, wouldn't she be prepared to be summoned? Possibly it would have access to such mundane magic as a potion of invulnerability to quaff before it was summoned?

Another thing to remember on Mariliths is that they get to parry one melee attack each turn in a round, so for each PC attacking it with a melee attack, it's first attack is versus AC 23.

But yeah, 8 5th-level PC's should blow through plenty of high level CR creatures that don't have lair actions.


Title? I don't need no stinkin' title.
I'll just echo what others have said, this was an easy fight so it's no surprise it wasn't a challenge.

If you have a large party, you have to beef up solos a bit.

Give them more legendary actions - my rule of thumb is 1 or 2 legendary actions less than the number of PCs.

Don't set up situations where they can be trapped and/or surprised (or account for it in your calculation). Getting to pre-buff increases the CR of the party by at least 1 or 2 levels, much less getting in a surprise round.

I don't use solos very often, but when I do I have lair actions (with a bigger group probably multiple lair actions) and the number of legendary actions can exceed the standard 3 since the rules are built around a 4 person party.


This may be somewhat orthogonal to the issue at hand, but how did 5th level PC's summon a marilith? I'm not up on the latest summoning stuff, but I'm not aware of a way to do this outside Gate (and you need to know the true name?)


For the record, I am not super upset about the Marilith fight, and I recognize the advantages they had in being able to prep (since I enabled it). My point is more that I don't really trust the CR system for 5E in general and specifically scaling it to a large party. It seems like action economy is the most important factor in combats and doubling the usual number of PCs is an exponential increase in capability. I am going to try and fix the way I operate as a DM, not try and "fix" the system.

What I will be interested to see in how a large group of less dangerous creatures affects play versus the big group. The PCs are about to accidentally walk into a hive of a dozen intellect devourers, and they have no idea.


It seems to me that, given she could spy on them via their items, she would have known about the plot and ambushed them while they were preparing (with minions in tow).

That said, I have found that solos are more impressive when they have a few minions with them (even if the minions are relatively inconsequential). Even the world's best quarterback wouldn't stand a chance against so much as a high school football team. But you put a great quarterback with a sub par team and he can make them shine (the same can be said of a great team and a sub par quarterback).


This may be somewhat orthogonal to the issue at hand, but how did 5th level PC's summon a marilith? I'm not up on the latest summoning stuff, but I'm not aware of a way to do this outside Gate (and you need to know the true name?)
In game details. It was a specific marilith (technically it was The Marilith but that's just because I like using creatures as unique) and the party reverse engineered her connection to the cursed items, yada yada handwavium.


I suspect a dozen intellect devourers will be deadlier, unless they are tightly grouped together and vulnerable to area affect spells. Also, depends on how great the party's saves are...

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