Long ago a Necromancer who's name has long been forgotten, experimented with ways of extending life.
His practices were non-conventional, and instead of trying to create magical life, he instead focused on parasitic magic.
The act of tethering one life form to another, and having the host sustain the person who's life was to be extended.
He failed miserably.
However, he did create a form of magic which did tether living beings together, but instead of sharing life, it shared pain amongst those who were connected.
He shared his knowledge with his followers, and soon a series of Rings called 'Unity' were created.
These rings are adorned with jewels that don't glow or refract in any spectacular way.
But when a wearer of the Ring is hurt in anyway, they will notice the pain from said damage being diminished by a fraction proportional to the amount of wearers nearby.
To prove his point to his followers, the necromancer fashioned ten rings of Unity, and distributed them randomly to his hall full of followers.
He detonated a large explosion in the room.
The people who wore no ring were incinerated outright.
Those who wore the ring however, shared each others pain in a network - and they were left with only minor singes to their bodies.
The ring however has also been used as a means of assassination.
When a King is too difficult to get to close to, with his guards and protectors, one can always smuggle him a Ring of Unity.
Give a second and third ring of unity to your followers, and then inflict enough pain and damage on them to bring them near to the brink of death.
The combined pain felt by the King would be too much for his body to bear.
Of course your followers will likely die too, but they can potentially survive if the proper enchantments are cast on them.
I am planning on making a new Reward Drop - Unity.
An ultra rare legendary item that when worn will provide a set of bonuses.
However, it will also have a hidden ability.
Damage inflicted on the wearer is divided by x, and shared among all who wear the ring nearby.
x being the amount of wearers nearby.
Eg: 3 People logged into Rhun, each wears the ring.
When one player is damaged for 100 damage, the damage is reduced to 33, and all three players received the damage.
This is good and bad.
Players will receive only 1/3rd of the damage when they are hit.
They will also received damage from other players, even if they themselves are not hit.