D&D 5E End of Campaign Encounter (help!)

I'm looking for suggestions for a challenging encounter for my campaign 'finale'. Any creatures/ ideas are welcome since I'll reskin it to match the campaign tone. I'm planning to have a large map on roll20, to let the PCs face some kind of minion troop before facing the proverbial "end boss". It's the first time they have characters at that level, so I'm trying to think something that will them give that epic feeling.

The encounter building at the dmg don't help at all at that level, I think. Specially when you have lots of mooks + bigger level monsters.

For the record, the party is:

12th cleric (life)
12th wizard (abjuration)
12th ranger (hunter-melee)
11th rogue (mastermind)/ 1st fighter
3rd fighter (still deciding)/ 9th warlock (fiend-blade)

Oh, for the record, they are going to a demiplane to stop an eldritch abomination from entering the material plane.

have a previous villain return as a head minion

What's the Eldritch abomination? A good, old-fashioned fight with an "aspect of evil" (a-la 3rd Edition) can make for an excellent final confrontation.

Perhaps get a map with a large pool of water with a uber (max hp, additional spells) aboleth in it. Give its tentacles extra reach. Mooks can be it’s slaves, such as mind controlled ogres. Party will have a tough time with it going under water then reappearing, dominating random PC’s. I know a similar encounter proved very challenging for my party of 5 at a similar level.

A beholder is another good option. Use zombies as it’s mooks.

I'd go for a beefed up Elder Oblex that rather than just gaining its enemies' languages and proficiencies when it brain drains someone also gets some choice class abilities and spellcasting. It gives you an excuse to use their favorite tactics against them. It can even create creepy ooze simulacra of each of them.

Adding up CR (with some modification) emulates most of the 5e encounter building systems. You should double CR from 11 to 19, and 5x from 20+, and CR 1 and under is a bit under valued.

Do the same for PCs (add up levels, with the same bonus for level 11+).

1/5 of PC level sum is easy.
1/4 of PC level sum is medium
1/3 of PC level sum is hard
40% (2/5) of PC level sum is deadly

...

But really, for a final epic fight, what I think you want is a bunch of chained encounters with no break between them.

Like, medium hard hard short rest medium easy deadly+.

That final split -- medium easy deadly -- can be waves. You have a medium wave, followed 4 rounds later by an easy wave, then the boss shows up 3 rounds later for a deadly.

60 total levels, with an extra 5 for L5+ and 10 for L11 and 12, so 75 points.

So the ratios of 75 are:

Easy: 15 (Single CR 12)
Medium: 19 (Single CR 14)
Hard: 25 (Single CR 17)
Deadly: 30 (Single CR 20+)

Using DMG, 5000 easy/10000 medium/15000 hard/22500 deadly XP

Now, the DMG has a problem in that there is a "step" from 5 to 6 PCs; at 5 it makes too-easy encounters, at 6 too-hard. This system has no such step.

It says easy is CR 9, medium is CR 13, hard is CR 16, deadly is CR 19. For everything except "easy" it is 1 CR lower than the above math (and DMG easy is ridiculously easy. A CR 9 monster against 5 level 12 PCs is toast on round 1 I suspect).

I like the beholder idea, they never faced one...

What if I use a Death Tyrant as the "eye" of the creature and two other monsters as his claws/ tentacles? Any ideas on what kind of CR I should be looking to those monster/ claws as to not overwhelm the party?

Buck_ said:

I like the beholder idea, they never faced one...

What if I use a Death Tyrant as the "eye" of the creature and two other monsters as his claws/ tentacles? Any ideas on what kind of CR I should be looking to those monster/ claws as to not overwhelm the party?

Click to expand...

Two grell with max hp along with the beholder should be challenging, especially if your party does not have good ranged options. The map can include pools of acid that the Grells can drop grappled characters in...don’t forget that the beholder should also have lair actions, making its CR higher.

Encounter in broad strokes:

at the entrance/path: mooks (a lot) - this is the main hide out, of course the big bad has lots of its mooks

At the main encounter:
Some mooks (just a couple that aren’t equipped for fighting as they were being helpers to what the big bad was doing - but there might be a on the side of the room a scepter or wand that if they get to it they’ll be more combative - giving the pcs the chance to notice the mooks will be more dangerous if ignored, thereby adding tactical choices)

The big bad itself. Remember his goal is to go somewhere else (the material plane) and given his role is likely more tactical to realize it doesn’t need to brawl just complete it’s mission to leave ( and close gate behind it ). So don’t fall in to the trap of forgetting motivation
The big bad also has a new option for its bonus action (trained arcana skill check, with advantage dc 15 ) success the gate is empowered by 1 step closer to opening

The gate should be there ( an archway? Or runic circle on ground , or Stonehenge like rock circle with embedded gems, or magic circle floating in the air through which the material world can be seen hazy but progressively getting more clear).
The gate requires 10 empowerings to open. The closer the gate gets, ham it up and have the big bad gloat about how soon the mortals will be but a footnote as the rest of the mortal plane will be full of his puppets/husks holding his power serving him.
If the bug bad knows the pcs personally and the players have established family members maybe the big bad starts calling them out by name to make it more personal


Two gems on sconces on opposite walls empowering the gate. Every round each gem gets the gate 1 empowering step closer. Gems are immune to damage that isn’t slashing, piercing, bludgeoning. Vulnerable to bludgeon. Is ac 5. After 50? Hp damage gem is destroyed. (adjust hp to level, each gem should be half hp of a creature of the level). If you want more gems then divide hp more such that total hp of all gems is the same as one monster. And it shouldn’t be capable of more than one/two gate empowerings per round. Maybe the gems alternate or go sequentially, etc

PCs can use a bonus action intelligence arcana dc 10 to understand how the gems are working
If they do that, they can then as a standard action use an intelligence (arcana) dc 15 skill check to reverse one empowering, as a standard action. Probably won’t be used much if at all but it’s an option if they start fiddling with the gems. Of course fiddling with the gems draws direct attention from big bad

After maybe 4 rounds when theplayers look comfortable in their tactics, have about four-five of the mooks (ready for combat) charging in from different directions ( if the players are bad off and you’re feeling guilty maybe they come from the direction the players come and are predamagaded as they some how survived and healed a little from that earlier encounter ). But basically some wave to make a new wave of enemies coming to shake up tactical decisions


ANyway just rambling how I’d do it. Everyone’s dm and group Style is different but maybe something in there will help