D&D 5E CR of a monster circumventing hit points?

[Quickleaf]

Imagine a sumptuous villain's lair – an evil cult leader, a rakshasa, a lich sultan – replete with ornate bronze oil lamps and perfume censers, diaphanous curtains, and fluffy silk pillows.

Now imagine all those objects are animated, including, yes, the pillows.

In fact, I'm converting Killer Pillows from DRAGON magazine! The way I'm envisioning them is that they function similarly to a Rug of Smothering except you can't speak while grappled & they don't deal damage. What differentiates them is (a) when you're grappled by a Killer Pillow you lose all held breath, and (b) when a grappled creature starts its turn, it reduces the number of rounds it can survive without air by 1.

How do I adjudicate this monster's CR? Specifically, its offensive CR?

Rules on suffocating from PHB for reference:

[SECTION]Suffocating
A creature can hold its breath for a number of minutes equal to 1 + its Constitution modifier (minimum of 30 seconds).

When a creature runs out of breath or is choking, it can survive for a number of rounds equal to its Constitution modifier (minimum of 1 round). At the start of its next turn, it drops to 0 hit points and is dying, and it can’t regain hit points or be stabilized until it can breathe again.

For example, a creature with a Constitution of 14 can hold its breath for 3 minutes. If it starts suffocating, it has 2 rounds to reach air before it drops to 0 hit points.[/SECTION]

So, conceivably, a Killer Pillow could knock unconscious a PC with Constitution 14 in just 2 rounds if not dealt with or circumvented.

It seems to defy the monster maths in the DMG. Would it be better handled as a trap? Or is there some math I'm overlooking?

 

[Ath'kethin]

I'm away from my books atm, but viewing the creature as a trap might be a better way to approach the conversion. I think it's similar to when I was working out how to do a Living Wall in 5e, and it occurred to me that the monster worked far better as a dungeon hazard than an actual monster. It follows a path set in 3e when the green slime morphed into a hazard instead of a MM entry.

So I don't have a specific entry to point toward in your case, but if you strip away the fluff from some of the traps (or hazards) you might find some mechanics that fit your needs.

 

[TheNoremac42]

Well... That's slightly horrifying. It's basically a fluffy facehugger. I would include that its "attack" hits, it can do a free grapple check. If it succeeds, then the suffocation can kick in. In terms of CR, I would put this probably a little above a mimic. I don't have the MM in front of me, right now, so I can't check what it's CR is.

 

[cooperjer]

Why would a character attacked by the pillow loose all held breath? As a player I would find this rule to be unrealistic and unfair.

As a DM I find it hard to make suffocation a threat in game play. I made house rule to help with that. In the case of the pillow I wonder how the pillow harms a character. Maybe the pillow begins climbing down the characters throat and up it's nose. This would make removing the pillows grapple harder. This would also make holding one's breath a little harder. So with that thought in mind how about this:

1. Escaping the pillows grapple is at disadvantage since it's climbed into the mouth and throat.
2. The duration a character can hold it's breath is decreased by 2d6 rounds at the start of the pillow's turn.

Feel free to modify the 2d6 to something that feel like the appropriate threat you want. More d6 is more threatening. A change to d4 is more consistent.

The damage output is difficult to judge. I would consider the damage equivalent of suffocating to be 2 to 3X valued as HP damage. Therefore 2d6 suffocating would be 4d6 or 6d6 damage per turn.

 

[Tony Vargas]

I'd think the pillows blinding you and keeping you from speaking would be quite enough given some other furnishings able to dish out real damage to a party of blind, mute adventurers...

Level does seem to translate heavily to hps/damage in 5e, because BA, of course. They don't do damage by themselves, so... IDK, traps/hazards/environmental effects/a spell cast by the BBEG? Silence & Darkness that you can momentarily escape with a good STR or DEX check.

As the party 'kills' the pillows, of course, the room fills with suspended down & fluff, which provides increasing concealment...

 

[Tony Vargas]

Imagine a sumptuous villain's lair – an evil cult leader, a rakshasa, a lich sultan – replete with ornate bronze oil lamps and perfume censers, diaphanous curtains, and fluffy silk pillows.

Now imagine all those objects are animated...

Upon further reflection, yeah, I have to use that someday...

, including, yes, the pillows.

"And, if they survive the soft cushions...

...the comfy chair!"

 

[MechaPilot]

Why would a character attacked by the pillow loose all held breath? As a player I would find this rule to be unrealistic and unfair.

Because most people don't ordinarily breathe as deeply all day long as they do just before holding their breath. A character holding her breath is probably assumed to have prepared herself, likely by taking several deep breaths, beforehand (the way real people do before swimming underwater or entering a smoke-filled room).

 

[Quickleaf]

Thanks for your replies Very helpful!

I'm away from my books atm, but viewing the creature as a trap might be a better way to approach the conversion. I think it's similar to when I was working out how to do a Living Wall in 5e, and it occurred to me that the monster worked far better as a dungeon hazard than an actual monster. It follows a path set in 3e when the green slime morphed into a hazard instead of a MM entry.

So I don't have a specific entry to point toward in your case, but if you strip away the fluff from some of the traps (or hazards) you might find some mechanics that fit your needs.

Yeah, in principle I agree with you, but my dilemma there was how to justify treating what are essentially Animated Pillows as a trap, when other animated objects in the room like a Rug of Smothering are defined monsters with HP & Antimagic Vulnerability?

Well... That's slightly horrifying. It's basically a fluffy facehugger. I would include that its "attack" hits, it can do a free grapple check. If it succeeds, then the suffocation can kick in. In terms of CR, I would put this probably a little above a mimic. I don't have the MM in front of me, right now, so I can't check what it's CR is.

Yah! Slightly horrifying is good! Actually...if you look at the Rug of Smothering, that grapples automatically if it hits. That's par for the course for 5e monster design. There's very very few cases of "hit, then make a grapple check"; all of the ones I've seen have been "hit, and the target is grappled (escape DC X)."

Why would a character attacked by the pillow loose all held breath? As a player I would find this rule to be unrealistic and unfair.

As a DM I find it hard to make suffocation a threat in game play. I made house rule to help with that.

Good question. Here's my reasoning. Look at the Rug of Smothering: "and the target is at risk of suffocation." I've seen that interpreted in two very different ways by DMs:

(1) PCs are always assumed to be holding their breath unless they're unconscious. So really the rug of smothering poses no great threat against conscious adventurers. It's much more of a resource-drain encounter OR a monster to be combined with other traps/monsters than reduce PCs to 0 hp and then the rug of smothering goes after the downed PCs.

(2) PCs are only assumed to be holding their breath when they're clearly prepared (e.g. about to dive into water or about to plunge into a room full of gas), otherwise (such as in the heat of a fight) their ability to survive without air is measure in rounds. In this case, the rug of smothering is a very scary thing in and of its own right.

RAW either of these interpretations could be right.

So my intention is to do a monster write-up that clarifies how it's supposed to be interpreted for the DM. I'm imagining a trait like this, derived from the assassin's Assassinate trait...

[SECTION]Breath-stealing. During its first turn, the killer pillow has advantage on attack rolls against any creature that hasn't taken a turn. Any hit the killer pillow scores against a creature that hasn't acted yet prevents the creature from holding its breath.[/SECTION]

The damage output is difficult to judge. I would consider the damage equivalent of suffocating to be 2 to 3X valued as HP damage. Therefore 2d6 suffocating would be 4d6 or 6d6 damage per turn.

Well, the thing is "2d6 suffocating" has no meaning in 5e. Suffocation circumvents HP. That's my dilemma.

By comparison, the rug of smothering deals 10 (2d6+3) bludgeoning damage...but that is it's own thing apart from the risk of suffocation, and could easily be interpreted as the rub crushing a creature's rib cage.

I'd think the pillows blinding you and keeping you from speaking would be quite enough given some other furnishings able to dish out real damage to a party of blind, mute adventurers...

True enough! Other design elements in this encounter for 15th-16th level include...

• A maelephant (CR 11).
• An intelligent Rug of Smothering (CR 2).
• Slaves, some of whom might have their own agendas complicating the scene.
• Diaphanous Curtains (CR ? trap?), animated objects inflicting forced movement and confusion.
• Killer Pillows (CR ? trap?), animated objects blinding/restricting speech/suffocating.
• A trap of some kind, still designing it.

Level does seem to translate heavily to hps/damage in 5e, because BA, of course. They don't do damage by themselves, so... IDK, traps/hazards/environmental effects/a spell cast by the BBEG? Silence & Darkness that you can momentarily escape with a good STR or DEX check.

As the party 'kills' the pillows, of course, the room fills with suspended down & fluff, which provides increasing concealment...

Hmm. Maybe the solution is not to use Animated Objects as a model at all, throw out the Rug of Smothering, and design it all as an elaborate trap...

 

[The Crimson Binome]

Challenge Ratings are supposed to measure the level at which the monster won't outright kill you from a single round of lucky dice. If this can kill someone in one round, then its CR would be equal to their level +1; there is never a level that you can reach where a couple of bad die rolls won't kill you.

 

[Jester David]

I suppose I'd look at it's defensive numbers for a base CR. The calculate the hp of an average adventurer at that level.
Them I'd figure out how many rounds it would take to smother one. Diving the maximum hp by that number give the approximate damage per round, which can be used to calculate the final CR.