I was thinking about simic hybrids with their grappling appendages and how they're kind of a pain to use for actual grappling. It would be so much easier if you could just use them like normal hands. This got me thinking about what a race or character with extra hands would look like, and what the value of such a feature would be. Thing is, I've designed such a race before, and I remember there being a lot of tricky things I needed to adjust to make it work how I wanted it to.

Now that I think about it, though, extra hands, using the rules as written, might not be as interesting as you might hope. The main thing I'm noticing is that it reduces the number of choices you need to make, as you have more hands to hold things and thus don't have to choose between them anymore. As an analogue, a character with only two hands is like a build that has to focus on one of three skill trees, e.g. warrior, mage, or thief, and as you add more hands it's like getting the second and third skill tree for free. Your build is no longer a choice, it's just about leveling up until you max out all three skill trees.

Real quick, to make things easier I'm probably going to use specific weapons as stand-ins for categories of weapons, e.g. referring to greatswords instead of typing out "two-handed melee weapons". Also, since it seems (not sure if any actual RAW exists) that you can change your grip on your weapons without spending any actions, I'm going to treat all two-handed weapons as if they are held in one hand and require an additional free hand to operate, and the same free hand can be used to attack with any two-handed weapon you're holding.

First, let's consider a creature with two hands. As noted above, here you need to make choices. Do you (a) go sword-and-board, (b) dual-wield, or (c) grab a two-hander? Each one has it's pros and cons, they're all good for different use-cases. It's up to you to decide which one is best suited to the particular situation (as well as your character in general, if you're investing build resources like fighting styles or feats). All are good at different things, so you have to pick the best one for the moment.

Next, let's look at three hands. Granted, three-handed creatures in fiction are very rare, as you usually skip straight to four hands. Now, we don't actually have fewer choices, contrary to what I said previously. But, what's going on is that we can take any two of the three options listed above and combine them. We can (a) use a shield while dual-wielding, (b) use a greatsword with a shield, or (c) dual-wield greatswords longswords (with the feat) (turns out the feat specifies "one-handed weapons", so it should work with a longsword being two-handed, but not a greatsword). While there are the same number of choices, these choices are actually less meaningful. When you can pick 2 out of 3 options, you only need for one of the two to be the correct choice. Of course, let's also not overlook that you're straight-up stronger than a two-handed character, e.g. getting the extra AC of a shield or the extra damage of a greatsword while a two-handed character has to pass on one of those.

Then there's the creature with four hands. There aren't really any choices any more; you'll always take a shield, and your only choice is between greatsword+longbow or double longswords. These are the optimal loadouts for such a character, and you're probably built around using one or the other already. Furthermore, we can see that there isn't much value added if we add more hands; a fifth hand allows the double longsword build to add a longbow or greatsword, and a sixth hand eliminates all choice entirely. Any additional hands beyond that only have situational use, e.g. grappling, or holding non-weapon items we need for whatever reason (scrolls, potions, keys, etc.).

Can we make some tweaks to this to make it work better? Probably. One change I was going to suggest was not letting TWF work with two-handed weapons, but the feat already doesn't allow this (though we could expand this to include versatile weapons being two-handed). Another change might be to impose disadvantage on attacks with a two-handed weapon while wielding a shield (because it "gets in the way", which sounds like BS to me but might be necessary for balance-reasons).

Another aspect of this is that it seems like a tweak should be made to the TWF rules. The iconic image of a creature with extra hands is to have them wielding many one-handed weapons, but there's just no reason to do that using the default rules, as you only get one off-hand attack. One option might be to add a Multiattack action, where you attack once with each weapon you are holding. It doesn't count as an Attack action, so it blocks you from using it with certain feats and such. Making e.g. four attacks with one-handed weapons vs. two attacks with a greatsword+shield also seems like a fair compromise, with neither being objectively superior. It does kind of shaft fighters, though, who already get four attacks.

An alternate solution to the TWF/Multiattack issue might be to allow you to replace one Attack action attack with two attacks from different weapons using the TWF rules, which would also still qualify for a BA attack. So if you have Extra Attack, you make your first attack with your "main hand", then swap your second attack for two different "off-hand" attacks, then use your BA to attack with your fourth and final weapon. For fighters then, they would just make three attacks with their main weapon, instead of one. Characters without Extra Attack, e.g. rogues, would be limited to three attacks that all must be with different weapons. Not sure if the attacks should add your ability mod to damage or not, I'm thinking not unless you have the fighting style.

It might also make sense to give a character with extra arms more item interactions, or possibly letting them draw/sheathe more than one weapon at a time (probably "double" rather than "one extra", so that the feat allows four weapons to be drawn at once, instead of three).

Anyway, what do you think? Do you think extra hands are more or less valuable than what I've laid out? What sorts of tweaks would you include on a multi-armed character?