Chosen Ones
From Dyos Wiki
The Chosen Ones are the only people who can touch The Gem and unlock its full power (though what this actually entails has never been fully explained). Their identities changes as the "plot" progresses. As revealed by the Convenient Plot Device at the close of DYOS X, the current ones are Choxorn and Taillesskangaru.
The Defender of the Universe is tasked with guarding the Chosen ones.
Selection
The identities of the Chosen are determined by the Gem, or, rather, by who or what ever created the Gem and "programmed" its rules. Usually, two are picked, in case something happens to one. The Chosen Ones have to be a DYOS contributor "important to the plot", and must 1. not be an evil villain, 2. not be likely to abuse the Gem's power and 3. be alive. The identity of the Chosen Ones will change if they no longer fulfill these and other secret requirements.
At the start of the Avatar Wars, the Chosen Ones were Judge_Deadd and e350tb. Kulade knew this, and hoped that by killing them he would gain their powers. His avatar minions were sent to do the dirty work, and the identities of the Chosen One shifted - though not to Kulade as he expected, but to Choxorn and Taillesskangaru. Kulade was only told later that he needed the Chosen Ones alive, but never got to know the identities of the new Chosen Ones.
Although lord_joakim touched the Gem and lived in the middle of DYOS X, he is not a Chosen One; why he was not destroyed by the powers of the Gem is unknown to date. He was, however, left with mutilated hands and caused some weird stuff to happen, so it's possible he has some other connection to the Gem.