My players (Level 6 in a homebrew setting) have defeated a Dao Genie in an underground dungeon. The Dao was trapped by a wizard long ago and had special wrist restraints (like the ones Genie wore in Disney's Aladdin), which dropped after the Dao was destroyed and turned to dust. The barbarian who is a kenku and likes shiny things decided to wear them because 'hey its pretty'.

So I never intended for these to be a cursed item but it seems like a fun idea and the party loves chaos (especially causing it). I had one idea of them being now tied to the Dao's genie bottle and gain the Bottle respite ability that genie warlocks get but it has this caveat that if someone else uses the bottle to put them back in (charisma save, maybe disatvantage?) and then back out they are under a charmed person effect, acting like a servant to the bottle user for one hour, making the save after an hour or when they take damage.

But I am worried about the potential abuse from this so as I am a newbie DM, any experts and veteran Dm's who can suggest any interesting or alternative ideas?

Given what their original purpose was, I'd have them do something like absorb/negate magic

So give the barb something like resistance to damage from spells and magic effects... but also any magical healing on them simply fails, as do other spells like bless, fly, haste etc. No more buffs from the wizard or cleric. Maybe after a certain amount of time wearing the shiny bracelets, all the barb's other magic items stop working too

The problem with making cool cursed magic items is that players love to turn them around and use them in creative ways.  AKA abusive.  Bottle respite is pretty powerful all by itself.   Just for the ability to store items (bag of holding) once a day at first level, let alone the hiding and safety.

I would instead suggest the player THINKS he gets the Bottle Respite ability, but actually just sits down and talks like a crazy man about how nice this bottle is and how safe he is in the bottle.

I’m personally a big fan of cursed magic items imposing additional Personality Characteristics (traits, flaw, etc.) on people. it gives the player something to RP as a curse, but doesn’t necessarily affect them adversely. It could be something as simple as the PC can’t take the cuffs off, and refuses to part with them, but the whole time they feel like a slave and a prisoner and yearn to be free. Something like that.

A cursed version of Dimensional Shackles might do it. The curse could be as simple as if you voluntarily put them on you cannot voluntarily take them off or try to escape from them and maybe have the wearer will also need to make a charisma save in order to voluntarily walk through an inter-dimensional/inter-planar portal.

So been reading the comment (thanks for the ideas) and I got an idea.

The shackles are connected to the bottle, where the bottle goes he will be pulled with it , example: if the bottle is thrown and goes further than 25ft the barbarian gets pulled for every five feet over 30 the bottle is thrown (bottle thrown 30ft, the barbarian is pulled 5 ft) with a DC 25 strength save to resist the pull... for one round, as it will try to pull the shackles back. It however does not ignore carry weight of the barbarian so someone carries the bottle and say flies away and pulls the barbarian with them it will count to the carry weight.

Also adding in a mental effect that the  barbarian wants to never touch the bottle and to give it to someone else to hold, this mental effect being a safeguard to prevent the dao from tampering with the bottle. 

second thought I might keep the mental effect but change the chain effect a bit

There are lots of possibilities.

However, if they were being used to help restrain the genie then I'd go with the suggestion of dimensional shackles (the character can't use any form of dimensional travel or teleportation - eg misty step, dimension door, teleport, planeshift etc do not work) and combine it with the effect of an Earthbind spell that prevents flying unless they succeed on a strength save every round. The interesting thing is that the curse isn't likely to be noticed for a while until they suddenly need to fly or teleport and find out that they can't. It also makes sense in the context of a djinni not being able to escape.

In terms of the djinni's bottle, I would have a separate curse associated with the bottle - if anyone decides to use it to rest or just to see what is inside, they find that they can't ever move more than 30' (or whatever distance) from the bottle and that they are unable to touch it or move it themselves or through anything they touch or use (no using mage hand to move it themselves). Only another creature can move the bottle.

I think two cursed items might make more sense than one in this situation.

P.S. The challenge with a "mental" curse in this situation is that the curse needs to have been restraining the djinni so you need to consider what sort of shenanigans would make sense (assuming they were being held against their will).

On the other hand, if the djinni placed the curse for anyone who stole from them then the curse should be pretty nasty and could be anything. Perhaps the character believes that the bottle provides a safe place to rest but the bottle only contains one hour of air. If the character long rests, they suffocate unless someone breaks the bottle from the outside. (or the character doesn't need to breath). Or perhaps, once in the bottle, they don't wake up (they are in a state of suspended animation) until the djinni comes home and utters a command word to free the intruder. Of course, if the djinni is dead, this is a bit problematic.

Quote from AntonSirius >>

Given what their original purpose was, I'd have them do something like absorb/negate magic

So give the barb something like resistance to damage from spells and magic effects... but also any magical healing on them simply fails, as do other spells like bless, fly, haste etc. No more buffs from the wizard or cleric. Maybe after a certain amount of time wearing the shiny bracelets, all the barb's other magic items stop working too

 alright, but consider an alternate functionaccording to the original legends of Djinn(from the real world), they were powerful destructive forces. howsabout this.

anytime the barb attacks a creture, the creture can make a Charisma check. on a sucsess, the barb has to make a Charisma save every time they attack said creature. on a failure, the sttack simply fails and the action is wasted. on a sucesss, they roll damage with disadvantage.

idk if this is to big of a nerf

Quote from IamSposta >>

I’m personally a big fan of cursed magic items imposing additional Personality Characteristics (traits, flaw, etc.) on people. it gives the player something to RP as a curse

you could have it so that the barb even finds it hard to be rude to people, or feels more benign, calmer

He can not longer speak out loud - good roll playing

He can only speak in a random language every day except common. - good roll play

this may help with the jinn not being able to teleport because he could not talk in his language to cast spell