Here's the Abyssal Sibriex From Mordenkainen's Tome

This....thing...is....AWESOME!

 

[Dausuul]

Are you saying this thing is fine as long as it's not one-shotted?

Are you saying a monster that loses half its hit points to the first enemy should stupidly stay and fight when it's obvious it won't survive a single round?

Or are you saying its abilities are so strong that once it gets to act it can be confident even a level 18 party won't hurt it again?

Grabbing them goalposts and running, aren't you? I was challenging the idea that "it won't live long enough to use its legendary actions." It clearly will, and as soon as it starts acting, it can make it much tougher for the PCs to slip in the rest of the damage.

As far as a level 18 party - of course they'll win against a solo sibriex! That's a Medium encounter: "A medium encounter usually has one or two scary moments for the players, but the characters should emerge victorious with no casualties. One or more of them might need to use healing resources." Considering that a sibriex can cast feeblemind and hold monster at DC 21 with its legendary actions, it certainly ought to deliver those scary moments.

For a deadly encounter with a solo sibriex, the party level is 12.

 

[Mr. Wilson]

Let's say we run into a ranged fighter that goes first. We'll assume the ranged fighter went straight fighter (BM) and are 13th level. We assume you took Archery style and Sharpshooter with your bajillion stat increases you are wielding a +1 longbow as your only relevant magic item. Due to the fact you're a fighter, you have a dex of 20 and go first because statistically it's likely you will.

Your attack bonus is +8 (+5+1+5+2-5), meaning you have a 50% shot of every hit landing. You go first and fire 3 shots then action surge for an additional 3 shots. That means 4 hits land on the first round (3 plus 1 more when you use precision attack to turn your closest miss into a hit with precision attack). You deal (1d8+6+10) x 4 damage to the boss (around 82 points of damage) on the first attack of the first round.

If you get lucky with your attack rolls and can use precision attack to turn all misses into hits, you deal just slightly less than lethal in the first action of the first round.

 

[Seramus]

A legendary wizard - that is, a solo monster - need several times as many hit points as a regular one.

Since a PC Wizard is not meant to enter dungeons alone, and in fact brings allies with the explicit job to protect the Wizard, your comparison isn't valid.

Legendary creatures don’t need to be solo. Especially not when they have minion making skills baked right into their power set. That’s a completely unnecessary straight jacket on encounter design. You’ve got an XP budget for a reason.

It’s not impossible for a Sibriex to get caught alone, for whatever reason, but engaging in the hobby of making new minions is literally called out in the flavor text. So they should almost always have minions around to help protect them.

 

[Tales and Chronicles]

Legendary creatures don’t need to be solo. Especially not when they have minion making skills baked right into their power set. That’s a completely unnecessary straight jacket on encounter design. You’ve got an XP budget for a reason.

It’s not impossible for a Sibriex to get caught alone, for whatever reason, but engaging in the hobby of making new minions is literally called out in the flavor text. So they should almost always going to have minions around to help protect them.

Also, demons have the variant to summon other demons right in the PHB. There's a lot of white room theorycrafting in this thread. Its like people really want to argue that: ''this monster is too weak for my party of fully optimized warriors who prepared the right spell, who just took a long rest, who engage this monster on a flat plain when he's alone and where we won initiative because reason. WotC reallt dropped the ball on this one''. In a real game encounter, the thing will be fought at the end of a twisted dungeon full of disgusting thing, with demons lurking in every corners. The party will then engage this demonic mastermind in a room of his choice, where he'll summon other demons as a last ditch move.

 

[UnknownDyson]

I've never understood why people always think they would encounter a monster (particularly a legendary) in a field or green room where its just you vs them. This is an obyrith, to even encounter it you would have to be in the depths of the abyss. It is so highly unlikely that you would encounter a creature like a Sibriex on favorable terms that complaining about it's hit points not withstanding the fighter action surge is nonsensical.

 

[Erechel]

Let's say we run into a ranged fighter that goes first. We'll assume the ranged fighter went straight fighter (BM) and are 13th level. We assume you took Archery style and Sharpshooter with your bajillion stat increases you are wielding a +1 longbow as your only relevant magic item. Due to the fact you're a fighter, you have a dex of 20 and go first because statistically it's likely you will.

Your attack bonus is +8 (+5+1+5+2-5), meaning you have a 50% shot of every hit landing. You go first and fire 3 shots then action surge for an additional 3 shots. That means 4 hits land on the first round (3 plus 1 more when you use precision attack to turn your closest miss into a hit with precision attack). You deal (1d8+6+10) x 4 damage to the boss (around 82 points of damage) on the first attack of the first round.

If you get lucky with your attack rolls and can use precision attack to turn all misses into hits, you deal just slightly less than lethal in the first action of the first round.

You are not counting maneuvers damage. +6 on average. Nor feats like Lucky nor Inspiration rules.

 

[Paul Farquhar]

One of the characteristics of intelligent monsters is they have lots of minions to fight for them.

Going up against a party of adventurers solo is pretty much the definition of low intelligence.

 

[MechaTarrasque]

And I'm not paying WOTC to write INT 20 in a box so I feel allowed to spend an hour prepping elaborate tactics for the monster.

It should all be in the stat box.

Its not that I won't ever prep. It's that writing the two numbers 2 and 0 in this particular field has no intrinsic value. I can prep a stupid monster or a smart one.

What doesn't fly is offloading the responsibility for making a monster deserve it's CR onto the DM.

High INT is worth zero extra CR. And that's exactly the way it should be. If it's not in the stat block, its not in the CR.

I believe the time you are looking for is "5 minutes", but that would take away from your 12 hours a day on Enworld.....

Then why don't you pay for someone on the DMs Guild to give you monsters the way you like or buy one of the numerous monster manuals from Kickstarter full of those kinds of monsters?
.
Please don't insult us by giving us the "I only trust what WotC provides", since obviously you don't.

 

[Dausuul]

Emi’s Sibriex from the dome of foes was posted by Mr Stewart!

Two obyriths enter! One obyrith leaves! Two obyriths enter! One obyrith leaves!

 

[77IM]

I've never understood why people always think they would encounter a monster (particularly a legendary) in a field or green room where its just you vs them. This is an obyrith, to even encounter it you would have to be in the depths of the abyss. It is so highly unlikely that you would encounter a creature like a Sibriex on favorable terms that complaining about it's hit points not withstanding the fighter action surge is nonsensical.

If the level 18 party has even an inkling of what they are up against in the sibriex, they are going to nova that thing into paste.

The only way it's dangerous is if it's the last of the mythical "6-8 encounters per day" or if there is some kind of serious terrain advantage that allows the sibriex to become straight-up untargetable on other creature's turns.

In both cases, it doesn't need to have Legendary actions or resistance to be a serious threat. I think Legendary should be reserved for creatures that are encounters unto themselves, because the "field or green room" no longer counts as "favorable terms."