Random encounter help needed

[KittenMagician]

the players in my campaign are gonna hit a zone soon that is being plagued by demons and evil aberrations. i want to have a table which i can roll on for random encounters of the ones i found that fit what im looking for. the help i need is a better understanding of the CR system. i will have 5 players @ lvl 5 and 2 dmpc's @lvl 6 at the start of the area. by the end of the area i want them to all be lvl 8 or 9. most of the demons and aberrations i have been looking at are between CR 1/8 and CR 8. i want to know if 5 lvl 5 players and 2 lvl 6 dmpc's would be able to take on CR 8 monsters so i can put them on a random encounter table.

[MikeRoxTheBoat]

A lot of the DMs I know use Kobold Fight Club to get a general idea of what could be a suitable encounter at certain levels for certain numbers of players. Then they customize a bit from there. CR in general is a little iffy, anyway, 'cause depending on party composition, optimization, and just luck with rolls, the difficulty varies quite a bit.

[Son of A Lich!]

the help i need is a better understanding of the CR system.

Oh, well, I think I found your problem.

Don't worry, this is a pretty easy fix.

Don't worry about the CR system - what you are trying to use it for is crap. It's not very good at proving a solid chance against your party, because players are always going to be too difficult to appropriately balance an encounter against based on a seemingly arbitrary number.

Is an Aboleth more powerful then a Goblin? Yes. Will an Aboleth kill a party of 5 level 5 characters?... Probably, but it's a bit swingy. Is the Aboleth alone? Does he have lair actions? Is he underwater? Etc. etc. This moves the "TPK" meter back and forth pretty drastically, before we include things like dice into the mix.

First, I would find a list of monsters you think would be killed individually if put infront of the players that fit your theme. Sure, a Minotaur isn't going to wipe the party and isn't literally an abomination of the Abyss, but you can refluff it to suit your needs.

Then, mix and match interesting things together - things that are complimentary to one another or have cool rule interactions. Example - Medusa (Look turns to stone, so avert your eyes) and living carpet (Player is engulfed, and no one is looking).

If the match is too much for your party to handle, you'll know on the table. Fortunately, evil is selfish and even if they could kill the party if they press forward, they're probably going to turn tail as soon as they get what they want. They were hungry? They killed the hobbit, and are going to find a quiet place to eat it. They are territorial? They stop attacking as soon as they killed the first party member and try to scare off the rest. They are looking for gold? They're basically hungry, and should treat it similarly.

Remember that these are random meetings - they have no real quarrel with the party proper. The party is just in a bad place and got in a little trouble.

[MarkVIIIMarc]

the players in my campaign are gonna hit a zone soon that is being plagued by demons and evil aberrations. i want to have a table which i can roll on for random encounters of the ones i found that fit what im looking for. the help i need is a better understanding of the CR system. i will have 5 players @ lvl 5 and 2 dmpc's @lvl 6 at the start of the area. by the end of the area i want them to all be lvl 8 or 9. most of the demons and aberrations i have been looking at are between CR 1/8 and CR 8. i want to know if 5 lvl 5 players and 2 lvl 6 dmpc's would be able to take on CR 8 monsters so i can put them on a random encounter table.

There are encounter calculators online. I LOVE THEM.

Do they work every time? Nope. Sometimes the PC, the DM or the Dice do crazy things. Sometimes the environment just favors one side or the other. Sometimes the party is fresh, sometimes worn out. You'll get used to it.

The best tool I have found for guestimating what is appropriate is CR.

FWIW, I find multiple smaller encounters in a day are more predictable than one encounter. For that one encounter to be interesting it will have to take them to their rested limits. The small encounters I can control as a DM and so can the party. That said, you'll want to find a comfortable number of rests to "allow" by putting time limits on things or promising reinforcements are coming for the bad guys or whatever.

[Vogie]

The first thing I'd do is Split the party. Get rid of the DMPCs, and leave the PCs to suddenly on their laurels. You can bring them back by the end of the encounters, but if the party had been relying on them for anything (tanking/healing/etc), that'll make the desperation feel more real.

If you have random encounters that seem too easy for the PCs, add things the party isn't expecting:

Undead Fortitude, (en)Rage, or Regeneration abilities. Nothing is more annoying than a "what do you mean they aren't dead?"
Patrols through the region after periods of time. The party can discover this and hide from them, but if they're engaged in a combat encounter, they may not notice that enough time has passed and now the guards are rounding the corner, and they're all in plain sight.
Skill challenges. Instead of the normal random encounters, throw in some skill challenges, making the PCs go on a merry chase, or cinematically fight through minions, or dodge, duck, dip, dive, and dodge through a series of crazy traps.

[Helldin87]

Another thing to factor in is casting. If your enemies are capable of casting and someone in the party isn't a counterspell bot then spellcasting has a way of leveling encounters out nicely. To balance this the Monster Manual enemies that can cast spells seem to have correspondingly lower HP and physical stats (makes sense but worth mentioning). Having a spell caster in the enemies makes it so that PCs have to actually play smart and really work to keeping it locked down. Cloudkill or even a simple fireball can be a real fart in the fruit loops for the PCs if not countered.

The first time I introduced a spellcaster enemy to my current PCs they were less than thrilled with how easily their HP started to slough off.

Make it more interesting: Have the enemy engage in summoning. The Drow Mage has an ability (not a spell) that lets it summon a shadow demon with 50% chance of success. Killing the mage kills the demon too, but do PCs know that? Maybe maybe not.

TLDR try some caster mobs.

[Kurt Kurageous]

Don't make them random. Plan every encounter. Then use the ones that you want to.

Consider two part waves. If the first wave gets swept, put in a second or a third. If the first wave is draining resources, then DON'T use the second or third wave. That way you won't mis-build and kill them, or fail to challenge.

I personally am too dense to figure out KFC. I use the guide from donjon at:
https://donjon.bin.sh/5e/calc/enc_size.html

Lastly, here's a splat of ideas.
Use the environment.
Use a countdown.
Use exhaustion.
Use spontaneous resurrection to 1HP, like delayed Relentless.
Or have them come back as something else. Zombies. Shadows, Specters, etc.
Give them resistance to something obvious, and vulnerability to something else.
RAW says that only special foes make death saves. So make your foes special.