There is a difference between a stable creature and a conscious creature. A creature that is stabilzed is one that is at 0hp and doesn't need to make death saving throws. Such a creature will regain 1hp in 1d4 hours at which point it will regain consciousness. This item doesn't bring you back into a fight, it prevents you from dying due to death saves.

Does this double just the die result? Or does is double the HP regained from spending the hit die? Hit die is the 1d# + CON, so its 2(1d#)+ CON or is it 2(1d#+CON)?

 

From the Short Rest rules: "For each Hit Die spent in this way, the player rolls the die and adds the character's Constitution modifier to it. The character regains hit points equal to the total (minimum of 0)."

I would rule that you double the HP regained, since the Hit Die restores hit points equal to the total. The Constitution modifier is not a separate hit point gain.

My warlock recently made a deal where he sold his blood and replaced it with magical ink. He can use his blood to make magic tattoos, but he can't regain hit points from spells anymore.

His first downtime activity will be to make himself a tattoo that replicates this item.

Quote from BadhandsBob >>

There is a difference between a stable creature and a conscious creature. A creature that is stabilzed is one that is at 0hp and doesn't need to make death saving throws. Such a creature will regain 1hp in 1d4 hours at which point it will regain consciousness. This item doesn't bring you back into a fight, it prevents you from dying due to death saves.

 On top of that, a 20 on a Save DOES bring you back into the fight... and this stops you from making Saves, potentially keeping you out more than it helps put you back in!

Ah yes, punish me for taking a item to keep me alive cause I keep going down. This item only stabilizes a player so they get 1 hp and are unconscious. 

On a short rest or when an ability or feature mentions it. For example the chef feat.

The equation would be. 

2(1d#+CON)

Being stabilized means nothing if you're unconscious. Also while you're unconscious you're prone so enemies can still attack you and they would have advantage to do so. This is like if you keep healing a downed player. No matter how much hp you have if you go unconscious and no one wakes you up you don't get up. You're just unconscious with hp.

As a DM, part of the beauty of this item is in finding a creative way to introduce it to your party. As a player, its finding creative ways to use it outside of combat.

Okay, but doesn't stabilizing reset your death saving throws? So if you get hit once while you're down, you lose two death saves. But on your turn you stabilize again, right? So you're back to 0 fails?

Okay, but they can't do anything while they're down and unconscious. If their team loses the battle they die. It does nothing, but make the fight elimination based.

But that means that nobody can kill you on their own, unless they have multiple attacks. No matter how hard they try, you'll continue stabilizing every single time you get close to death. You would need two people working together in order to actually put a person wearing this thing down, which just seems ridiculous. At that point, the character will never die UNLESS it's a TPK, or the party has to flee and leave their forever transitional-state body behind.

Have you considered that one character might die even if not a single one of their allies has even taken damage yet?

Not quite.

There's ways around that.  Easiest way is just take it off the character while they are unconscious.  Since its uncommon it's likely many intelligent foes have a good chance to recognise what it does.  Suffocating the character is another example.  It really isn't overpowered.  If a player wants to use a precious attunement slot just to be stabilized into a helpless state, that's a fair trade.    It doesn't need nerfing or balancing.  

I was thinking this exact thing! So many people in this thread are like "wow, people will be stabilized every turn, they're literally unkillable." Which would be true... if it wasn't so easy to take off!

While this item might make the party less stressed out when a member goes down, I don't think it really has the power to change the course of a combat. If someone wearing this goes down, they can't help their party. If a player's whole party goes down, they're screwed anyway. I think this is a pretty balanced magic item.

it doesn't use the hit dice to heal, does it, I read it as saying that when you do a short rest and use hit dice to heal, the periapt means you double the number rolled???

It's nice, but it doesn't make you invulnerable. A warlock with repelling blast could send you off the edge of a cliff. You die instantly from massive fall damage. A wizard could cast disintegrate on you. Congratulations, you're a very stable pile of dust. You could also get hit three times before the start of your next turn.

Twice before the start of your next turn

Quote from Silverwave21 >>

Twice before the start of your next turn

 "If you take any damage while you have 0 hit points, you suffer a death saving throw failure. If the damage is from a critical hit, you suffer two failures instead. If the damage equals or exceeds your hit point maximum, you suffer instant death."

So three regular hits, or two crits, or one massive hit that does more than your maximum HP.