Users[]
The only user of the Dark Emerald is Sonic the Hedgehog, as he is the only being able to manipulate negative chaos energy, which is the only energy the emerald contains.
Wielders[]
This item is the very life force of Sonic and allows him the Chaos abilities he has, and has yet to discover. If the Chaos Emerald was to be separated from him, Sonic would die. It had affected his genetics and made him to be a true living Chaos Emerald. While it is by far the most powerful emerald, it also has its side affects. It can cause Sonic to hear voices and it often tries to corrupt him. It can also cause him to become very sick, almost to the brink of death, but it doesn't happen often. Sonic hates the fact that he has to rely on such a corrupt item, and uses it only under extreme circumstance. It also will cause him to go on a rampage if he doesn't hold back from using his power, so he has never used his full power.
Powers[]
The Dark Emerald allows the user to be able to achieve a mini superstate, only it doesn't last as long and it causes the user to become the very definition of chaos, and will cause them to go on a rampage if not used properly. This also allows the user to use any other Chaos type move, only the energy will be black and is much stronger. It also gave Sonic immortality, and his super speed.
History[]
The Dark Emerald was first created when the Master Emerald was created. It's purpose was to contain and valence all the negative chaos energy the Chaos Emeralds couldn't hold, while the Master Emerald mostly contained the excess positive energy to balance. It was so power and dark that it was said to have been cursed. Tikal eventually sealed it to where it can not radiate any energy, as it could corrupt any person who came in contact with the emerald.
Four thousand years later, the Emerald was unsealed and somehow was given to Queen Aleena, fashioned to have looked like a necklace. The emerald rearranged Aleena's genetics, and also Sonic's, as she was pregnant with him at the time. Because the Emerald messed with both of their genetics, it caused Sonic to have been born prematurely, and very ill. That then made the queen seal the emerald within Sonic so that he would live like what was prophesied about the child of Aleena.
Because the first type of energy a Chaos user is exposed to for their first time effects what type of energy they can use, Sonic's first taste was negative energy. That caused much problems in the future of the hero, and the emerald in him became his life force, should it be separated from him, he would die.