Avoiding the "invisible jet" effect with a shadow mastiff mount

Question

One of the player characters in a game I run is a halfling rogue. I want to give her a non-evil shadow mastiff as an intelligent mount due to synergy with her rogue features. This is a case where the Rule of Cool will bring my player some happiness and a unique edge, so I am not interested in being told I am wrong for trying this (even if I am). Rather, this question will be about a matter of balance.

The shadow mastiff has a feature called Shadow Blend, described as follows (Volo's Guide to Monsters p. 190):

Shadow Blend. While in dim light or darkness, the shadow mastiff can use a bonus action to become invisible, along with anything it is wearing or carrying. The invisibility lasts until the shadow mastiff uses a bonus action to end it or until the shadow mastiff attacks, is in bright light, or is incapacitated.

Since the rider does not count as a thing being worn or carried, the rider does not turn invisible with the shadow mastiff when it uses this feature (as affirmed by a related question). Therefore, using Shadow Blend as written leads to the case where a rider mounted on a shadow mastiff stays visible while its mount becomes invisible, and that strikes me as silly and immersion-breaking. Let's call that the "invisible jet" effect after the appearance of Wonder Woman's invisible jet.

How can I effectively avoid the "invisible jet" effect when a shadow mastiff is being used as a mount?

I am looking for a GS/BS answer describing a house-rule that modifies the text or interpretation of the Shadow Blend feature just enough to avoid the "invisible jet" effect.

However, it needs to have been tested at a table in similar circumstances (relating to any sort of invisible mounts, not necessarily to shadow mastiffs in particular) and confirmed to be balanced and effective by reasonable metrics.

Answer 1

Describe it differently

The crux of this seems to be "Wonder Woman's Invisible Jet is silly," which is an issue with the fiction the rules inspire. I agree, it's a pretty silly thing to have to imagine. In this case, though, let's ask ourselves the question: do I have to imagine it that way?

We're talking about a beast that blends with darkness and shadow, not a wizard's Invisibility spell or a Predator cloaking device. If the whole problem is the idea of a halfling awkwardly floating above the ground, legs akimbo — well, imagine something else.

Describe it as "I'm riding a smokey blob of shadow," or "I'm riding a weird beast-silhouette with edges that waver like dark fire," or "I'm riding a regular ol' dog but its coat blends so well that you can't figure out where the dogs ends and the shadows begin til it's in full motion jumping out at you like RAWR." I promise nothing important will break if you say that you can't literally see through the big magic darkness-blending shadow-dog to the rider's leg on the other side.

Mechanically, you don't need to change much: the dog is still "invisible" as far as the rules are concerned, and the rider isn't. Feel free to describe being able to sorta make out the dog's shape or presence while it's got a rider, since just seeing the rider is enough for enemies to know its location and take a swing at it even if it's invisible. Feel free to describe how the rider is partially obscured by the dog's fur or its aura or whatever, but you can see most of them pretty clearly (that doesn't require special mechanics any more than "this broad-brimmed hat I'm wearing casts a shadow over my face" requires special mechanics).

There may be some small points where the mechanical and fictional description diverge, but in my experience that'll happen with detailed rules for seeing things in D&D across editions anyway. Just invoking the detailed concealment or invisibility rules has a tendency to bring out goofy edge cases.

(Experience: that's how we've treated shadow-creature shadow-invisibility whenever it's come up across different editions of D&D and it works pretty fine. Not transparent, just impossible to isolate from their environment.)

Answer 2

Short answer? There's no way to make it work. You can't have the rider invisible and unbalance the game, and you don't want to have the rider stay visible while the creature is not. Aside, why have you decided to give the character a shadow mastiff as a mount? My impression is they are not the sort of creatures that would agree to be mounted. Perhaps you're striving for the unattainable.

I would not count the rider as something carried. The intention of the wording is that the mastiff will not be given away by clothing or goods carried. Clothing and luggage can be considered an extension of the mastiff's body, therefore it is rendered invisible. A rider is not an extension of the body, it is a conjoined party.

On top of this, you yourself have admitted that giving easy access to invisibility would be a trouble mechanic to balance. So go with the easy ruling.

You don't need to explain yourself to your players. The first time the mastiff turns invisible, the rider doesn't. The players can ponder why all they want, its a mechanic of your universe. If the rogue doesn't understand in-game why they are not rendered invisible as well, there's no loss. Not everything needs a nice clean answer. Some things can just be.

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The answers to the question Sdjz linked are also an excellent resource.

Answer 3

Out of sight, out of mind... or not

I would actually suggest allowing the rogue to look silly sitting fully visible on an invisible mount, but only as a consequence of failing a stealth check.

Whenever the mount becomes invisible, which presumably if the rogue is riding it is when they both wish to go unseen, have the rogue make a stealth check (with advantage if the invisible mount provides some sort of obscuring quality or with disadvantage if being mounted restricts access to hiding places)

If the check is successful then the rogue blends into the shadows with their mount, and as nobody can see them nobody needs to know how they look (just don't describe it).
If they fail, not only do they look silly but they have also revealed they are sitting on something invisible.

It's up to your own interpretation if this maintains realism. The silly aspect is still there, but it's now tied to the rogue making a mistake and looking silly because of it rather than just a quirk of the world.

This should be balanced enough by tying everything to the rogue's stealth skill with a bit of a heavier consequence for trying to sneak with the mastiff.

It also provides a choice to your player:

1. Do they dismount and sneak separate to their mount to avoid both being caught simultaneously and to take full advantage on the mastiff's superior stealth while in darkness?

2. Or, do they risk remaining mounted to get through an area quicker?

Answer 4

Restrict the feature so it does not work while mounted.

I think the answer is pretty simple, I would house-rule that the shadow mastiff can not use Shadow Blend while mounted, and the invisibility is lost if mounted after using the feature.

This allows the feature to stay and be used in most other cases as normal, but completely excludes the absurd situation you don't want to have. It's not even hard to justify lore-wise. If you look at Shadow Blend as being a skill, to hide in the darkness, then having a large and heavy humanoid on it will make it rather difficult to sneak around stealthily. If it's a spell-like ability just say that it lacks the ability to affect such a large mass as an additional humanoid, and the spell fails if it can't affect the entirety of the shadow mastiff. Either way it seems a pretty simple hand wave.

However, I would point out that having an intelligent mount able to turn invisible is a potential issue in itself. I'd be careful of allowing them to send the mastiff off to do things the party members can't due to it's invisibility, Even the fact that the rogue can take his mount with him on sneaking missions, effectively being able to jump on a mount whenever he needs speed even if he had just been sneaking past people a minute earlier, is a bit of a utility buff.

Answer 5

Rogues are excellent at stealth as well. I’d just roll for the one with the lower Stealth modifier and decide if both are visible or not when the rogue is mounted. A little common sense would illustrate that the least stealthy of two creatures together are going to be seen if an onlooker's Perception allows.