Can Alter Self be used to enter an enemy's body and destroy it from the inside?

Question

I’m a new DM, so I’m using a starter pack with a storyline, although I have adapted it a fair amount. Earlier today one of my players decided that he can use Alter Self to create a tentacle which he can use to enter his opponents through their mouths or other holes. Once inside them he says he could just wiggle the tentacle around and squish their internal organs.

I’ve tried arguing that it can’t be done by that spell, but him and some of the others say that it can and it’s really just semantics at this point. Also, I do want to encourage the players to be inventive and I really want them to have fun, but I feel like this is game breakingly over powered. Any advice on how I can limit it or anything else I can do? Please

Answer 1

I think your players need some help understanding the game's fundamental abstractions. To that end, let's address their plan:

Sounds like a pretty reasonable way… to deal 1d6 damage

In reality, human beings have some pretty sophisticated tools for rearranging each other's internal organs in order to quickly cause incapacity or death. One such tool is a "sword."

In Dungeons & Dragons, that awesomely lethal tool does, like, 1d6 or 1d8 damage. Which is also, in many editions, enough to kill a starting character in 1-2 hits.

If you don't mind, I'm going to borrow a bit of text from a prior answer about a similar instant-win strategy using poison:

I'm not saying you should block the players by going out of your way to make it weak and useless. But don't make a game action super-powerful just because it could kill someone in reality. People were killed with regular ol' run-of-the-mill arming swords all the time. Yet they still do only 1d8 damage in D&D. Players characters and antagonists in D&D very quickly become more like action-movie heroes (or wuxia/super heroes, even) than real-world people as they attain levels or Hit Dice.

Something that should kill a regular person can, by all rights, do 1d6 damage in D&D. As other answers have already noted, the Alter Self spell already has a "natural weapon" option that will do just that!

Answer 2

That's not how attacks work.

The Alter Self spell could plausibly give the caster a tentacle that they can use as a weapon.

Natural Weapons. You grow claws, fangs, spines, horns, or a different natural weapon of your choice. Your unarmed strikes deal 1d6 bludgeoning, piercing, or slashing damage, as appropriate to the natural weapon you chose, and you are proficient with your unarmed strikes. Finally, the natural weapon is magic and you have a +1 bonus to the attack and damage rolls you make using it.

However, there is no mechanic in D&D 5e for using a natural weapon to instantly kill another creature, let alone use a natural weapon to enter another creature's insides. The system has rules for combat and attacks, and what your player describes is not part of them.

If the caster gains a tentacle via Alter Self, then attacking with that tentacle uses the rules for Making an Attack, which is described in chapter 9 ("Combat") of the Basic Rules. In summary:

1. The character chooses which creature, or object, or location they want to target.
2. They attack by rolling a d20, adding relevant modifiers, and comparing the total against the target's AC. They may have advantage or disadvantage based on the circumstances.
3. If they succeed, then the attack is resolved. They roll dice and add modifiers to determine the amount of damage dealt to the target. After taking damage, the target may still have hit points remaining, in which case they are probably not dead.

Beyond that, there are some other ways to use weapons, such as grappling, but none involve entering another creature as some horrific instant-kill device. It sounds like your players either do not understand the combat mechanics, or they expect you to let them do what they want. You are the DM, and if you don't want this sort of exploit in your game, then enforce it by saying no, and instead talking with your players about the rules that you want your games to follow.

Answer 3

Alter Self can't do that (That's what hit points are for).

On page 212 of the Player's Handbook, the relevant part of the spell description of alter self reads:

You grow claws, fangs, spines, horns, or a different natural weapon of your choice. Your unarmed strikes deal 1d6 bludgeoning, piercing, or slashing damage, as appropriate to the natural weapon you chose, and you are proficient with your unarmed strikes.

Nothing here says that you can deal some kind of instant-kill, mega-injury, or damage above 1d6 with their natural weapon. If the player wants to try that, they're doing something not covered by the rules, and Dungeon Master Guide p.4 explains how to adjudicate situations which are not covered by the rules:

As a storyteller, the DM helps the other players visualize what's happening around them, improvising when the players do something or go somewhere unexpected. [...] And as a referee, the DM interprets the rules and decides when to abide by them and when to change them.

In other words, the DM decides whether the players' wacky ideas actually work or not. Whether or not this loophole works is entirely up to you, the DM.

I wouldn't agree with your players in this case. Saying "we can just use a tentacle to strike their internal organs" is somewhat like saying "we can just stab them in the eye with a sword and kill them instantly". Sure, it has a certain logic, but D&D doesn't quite work that way. Enemies have hit points, and these must be depleted by dealing points of damage before the enemy can be killed.

Answer 4

This violates the simulated realism of the game world

In case you want a better explanation for why your player can't do that than just "The rules don't allow it", explain to him how he's ignoring just how difficult it is to perform the described manoeuvre in a combat situation.

First off, the orifices of a human body are difficult to enter, and several have active defence mechanisms, because something unwanted trying to enter the body through an orifice is a problem as old as air-breathing organisms.

Secondly, the enemies don't just stand still and wait for that tentacle to crawl up their leg and inside them. They'll try to jump out of range, rip it off them, slash at it with their weapons, and so forth.

In other words, "I stick a tentacle into you and rearrange your internal organs" is, just like "I stick a sword into you and rearrange your internal organs" something that your opponent is actively resisting, and therefore not doable with perfect accuracy.

And then you can tell him that this chance to manage to stick your weapon into an opponent (whatever it may be) is exactly modelled via AC and To-Hit roll. His exploit isn't an exploit because his approach hasn't invalidated the reality the To-Hit abstraction is modelling.

If he still insists, and you're feeling adventurous, then propose him an experiment: The two of you stand a meter apart, and he has to put his right pinky into your nostril (because that is basically, minus an Alter Self, what he wants his character to do with your characters), while you can do anything you like to stop him (because that is what the opponents will be doing). He's got 20 tries. Only if he manages to do it perfectly on every attempt, then he gets to do the manoeuvre in-game without a roll, too.

Once he accepts that, you can sit down with the rulebook and go through the options given for Natural Weapons to figure out how to stat out the tentacle in a way that makes you both happy.

Answer 5

In D&D 5e spells do what they say they do. Alter Self does say that the caster can "grow claws, fangs, spines, horns, or a different natural weapon of your choice"_{PHB 212}, and it provides statistics for those attacks which are very reasonable for the level. Limiting them to the statistics in the book seems like a good place to start.

Also, it's worth mentioning, that you are the dungeon master, and you have final say about how things work at your table, most commonly outside the explicit rules. If you don't think a tentacle is a viable weapon, or are not comfortable with this being a common occurrence in your game, it's perfectly reasonable for you to decide that at your table.

If there is a comfort issue, I'd also recommend taking that up with your players directly, to avoid confusion, and help set up an enjoyable game for everyone, including you.

Answer 6

I think in terms of balance, the Orifice-invasion Tentacle Kill is probably harder to accomplish than you'd think.

You're trying to use an unfamiliar limb to thread the needle and shove it inside a person's mouth when they're actively dodging and trying to avoid it.

Contrary to Hentai, this is pretty tricky to do.

The victim will be trying to block it, will attempt to pull it out if you're on target and then you'll have to actually "swirl" it to inflict real damage, which takes strength and leverage you probably don't have much of.
Realistically it'll hurt them a lot but probably not be lethal immediately even if you successfully puncture something internal.

It's not going to be easy at the best of times.
Make the player work for it and reward them if it works

The victim can try to block it, parry it, even slice the limb with their weapon.
They clamp their mouth down to stop the tentacle getting in
They bite down on the tentacle to hurt you
Heck, you're focusing so hard, they get in an easy strike with their sword on your body!

If the player somehow carries off all the rolls, take great pleasure in describing the horrifying results. They did this because they wanted a cool kill, not because it's effective, as has been noted, generally sticking a sword in someone will do the job much more easily.
If it's difficult but awesome, they'll use it when they think they can get away with it, not all the time.

Answer 7

As explained in other answers, the rules really cover what kind of damage the tentacle can do. If you want to play D&D, you kinda have to stay within the bounds of the rules, otherwise it's not D&D any more.

If you want to keep this particular (rather juvenile, if I may say so, but there's nothing wrong with that, if everybody including you wants that) mechanic, then there are two ways:

1. Turn this into balanced house rule. Something like, the tentacle needs to hit to, ahem, enter the victim. Victim should also get a saving throw to just get a "slap on a cheek" . Even on success, it does no damage that turn. Then next turns it could do 2d6 damage, attack roll against AC10+CON bonus. So if you succeed, you get to do a lot of damage, but if you fail, you do nothing. You could ask a house-rule balance question about the exact wording of your rule if you really want to fine-tune it.

2. Move onto more free-form, storytelling based gaming style. This won't be D&D any more, really, and requires a lot from DM and all players, and needs to be very co-operative, because rules won't support you much any more. If anything goes, you must trust each others to not do "I quickly stab the everybody in the eye" kind of things.

Answer 8

Sounds like a fair thought experiment

As you are the DM you can deviate from the rulebook. Let's see how the action goes down step by step:

1. To shove the tentacle into the orifice sounds like a full turn action
   The action seems long enough that the enemy can land a damage after showing but before you pulping the organs.
   In order to land your tentacle specifically in their mouth you need to circumvent all their defenses, as in critical hit.
   Different orifices are out of the scope here, but generally it seems like a precise and time-consuming move.
2. Entering the orifice you trigger a clench/gag reflex outside the normal action.
   I would count it as a penetrating (wedged unarmored limb) unarmed melee attack, if it succeeds then in addition to the damage they remove your tentacle from their orifice.
3. If your limb is still in the orifice, the enemy has an attack turn, where they probably attempt to penetrating attack your tentacle. If the attack is performed by biting/clenching, the same rules apply as in the instinctive reaction.
4. If by the start of your next turn you are still alive and your tentacle is still inside them, you can do an unaimed attack for a slightly higher damage than normal or an aimed attack triggering Step 2. beforehand and needing a crit to succeed (aiming for the heart of the creature with a limb you don't normally control sounds a lot like trying to fish out a ring from behind a sofa blindfolded).

If your players are still risking it, it sounds like an epic way to get killed by a goblin.

Answer 9

It's great that your players are being creative and thinking outside the box! But because we're the the DM, let's just help them fit their idea inside the game rules that you all have agreed to follow.

The rules for Alter Self state:

You grow claws, fangs, spines, horns, or a different natural weapon of your choice. Your unarmed strikes deal 1d6 bludgeoning, piercing, or slashing damage, as appropriate to the natural weapon you chose.

A tentacle is just a different natural weapon, and the way they want to use it is just flavor.

When your players attack with a sword, why can't they just say they cut their opponents head off? Because they are in a fight. Of course your player is able to cut people's heads off in a single strike: he is a skilled fighter with years of training that have killed countless people bla bla bla. But why don't they? Well, they would have, had his enemy not dodged his sword at the last second, making what would have been a fatal blow a mere scratch, explaining why he, in game, only took 4 points of damage.

I'm assuming you and your players have agreed that the tentacle is small enough to fit inside a human's mouth. If not, whatever, maybe its squishy. Describe the fight, how your players are trying to kill their opponents, but how the circumstances of the fight don't let them. Maybe they did get the tentacle inside the enemy's throat, but they were pushed right before they could smash any organs. Still, the opponent is left coughing blood. Maybe the enemy closed his mouth at just the right time, and the player ended up hitting him in the mouth, breaking some teeth.

At one time, describe how the player went for the eye, and successfully ripped it off. Just don't let them succeed twice, or you'll have given your players a free blind without any spells or... or do it if you want to, if it feels right for your group and your style of play.

And when they finally give that final strike, sure, describe how they put the tentacle inside the enemy's mouth and blow their stomach, grab whatever other organs you can think about and smash them against their bones. Write it ahead of time, so you can give them a clear image of the brutality (and honestly, gross) of their kill. Once you have described it once or twice, they'll be satisfied, and you can go back to saying "yeah, you attack with your tentacle and deal 1d6 points of damage".