The Viper Blade is a cool weapon concept I thought of a while ago. I just finished making it, and I love how it turned out, but I have one question. I put it as Rare, but should it be Uncommon or Legendary instead? And should I adjust the damage at all?

*Updated the viper blade.

That’s a tough one because if it dies it stops being a magic item any more, and a poisonous snake isn’t very durable, but it’s got the pseudo-familiar power too. I would probably say Uncommon as it is. However, if you changed it so that it reverts to a sword if it dies, then I would say Rare.

I feel like the Viper Blade is too easy to kill as a snake, so I made this updated version.

A long thin blade of serpentine design. Its blade poisons the blood of its victims (creatures without blood are unaffected.)

As an action, you can use the blade to transform into a Giant Poisonous Snake, which you control, for up to an hour at a time. You can see what the snake sees. You can distinguish this snake from others, and as an action, you can pick it up to turn it back into a sword. You can use this action once per long rest.

If you fail to transform the snake back into a blade when one hour is up, it will become a blade again wherever it is currently. The blade cannot transform again for 8 hours. If the snake dies, it becomes a Broken Viper Blade.

A Broken Viper Blade cannot transform into a snake again, and its poison damage is reduced to 1d4.

Two thoughts:

1. Since you can only turn the blade into a snake “once per long rest” as per the first paragraph of rules, there’s no need to state that “the blade cannot transform again for 8 hours” in the second paragraph of the rules.
2. You mention that a Broken Viper Blade has its poison damage reduced to 1d4, but nowhere did you state that the unbroken blade does any poison damage at all anywhere else. If the regular blade does poison damage (or applies the poisoned condition) you need to specify it in the description.

Fixed.

Do you have the new link?

Never mind, I see it.

Weapon (longsword), rare

A long thin blade of serpentine design. Its blade poisons the blood of its victims (creatures without blood are unaffected.) It deals 1d8 slashing and 1d6 poison damage.

As an action, you can use the blade to transform into a Giant Poisonous Snake, which you control, for up to an hour at a time. You can see what the snake sees. You can distinguish this snake from others, and as an action, you can pick it up to turn it back into a sword. You can use this action once per long rest.

If you fail to transform the snake back into a blade when one hour is up, it will become a blade again wherever it is currently. If the snake dies, it becomes a Broken Viper Blade.

A Broken Viper Blade cannot transform into a snake again, and its poison damage is reduced to 1d4.

Notes: Melee Weapon Attack: Slashing, Weapon Property: Light, Damage: Poison, Poisoned, Damage, Combat, Versatile

I see that you based it on a longsword, so you don’t need to state it’s normal slashing damage. Looking down at the notes at the bottom I also see that you left it as a versatile weapon (meaning it does 1d10 slashing when used with two hands), but also added the light property. Did you intend for it to be able to be used with two hands? Making a longsword light is a little odd, and pretty powerful because it allows anyone to use it with two-weapon fighting. A light d8 weapon should have a higher rarity. I also see in the notes that it says “Melee Weapon Attack: Slashing,” which I think means you might have added a Modifier to make it do slashing damage, which you don’t need to do because it’s already a longsword.

You could simplify this item, clarify it, and make it fall a little more in line with the official material if you reworded it slightly. Try something like this:

Weapon (rapier), rare

This long, thin blade of ophidian design is as venomous as the serpents that it resembles. On a hit it deals an additional 1d6 poison damage.

As a bonus action you can speak this weapon’s command word to transform it into a giant poisonous snake for up to one hour, at the end of which time it reverts back into a sword. The snake is friendly to you and your companions, and you can issue it verbal commands on your turn (no action required). In combat it shares your initiative, but takes its turn immediately after yours. If the snake dies, it automatically reverts into a sword. While the snake is within 60 feet you can use your action to sense what the snake senses until the start of your next turn, during this time you are blind and deaf to your own senses. You can distinguish this snake from others, and as a bonus action you can repeat this weapon’s command word to turn it back into a sword. Once this weapon transforms into a snake it cannot do so again until the following dawn.

That simplifies things, while also covering more situations, and clarifies a bunch of stuff. Wadaya think?

I don't know why it says light, that was probably accidental.

But that's helpful. Updated Viper Blade.

Honestly? I think this would be better if it just turned into a regular Poisonous Snake. Since having it fall in battle means that it permanently breaks the weapon, then having it turn into a more combat-capable form isn't really that much of a boon, since you're going to want to avoid using that in combat as much as possible. It'd be much more valuable to have it transform into a tiny snake that can sneak into places or that might not draw as much attention as a giant snake would. Unless, of course, the idea is that the larger snake is meant as a balance to the weapon to keep it from becoming too valuable.

Quote from TransmorpherDDS >>

Honestly? I think this would be better if it just turned into a regular Poisonous Snake. Since having it fall in battle means that it permanently breaks the weapon, then having it turn into a more combat-capable form isn't really that much of a boon, since you're going to want to avoid using that in combat as much as possible. It'd be much more valuable to have it transform into a tiny snake that can sneak into places or that might not draw as much attention as a giant snake would. Unless, of course, the idea is that the larger snake is meant as a balance to the weapon to keep it from becoming too valuable.

 That is a good point. Better for spying. You wouldn't use the snake much, and it's not like everybody's top priority is to kill some random snake, and it can just hide in a small crack...

I might change that again, actually.

*Fixed, again