For untold eons the existence of a legendary artifact that grants it's user ultimate power has tempted many amongst the elder space faring races with the lure of universal conquest. But many whom have attempted to take the relics power were beset with a test of character hidden throughout it's citadel which dragged any and all spelunking hunters into idyllic fantasies that left them as dust in the wind. The brave few whom had managed to bypass such an alluring trap were often found unfit by the Crystal and as a result, had the genetic potential of change and growth in their entire species halted as a consequence.
A myriad of different racial figures standing guard as unmoving sentries before the waiting items stronghold standing as testament to their failure to meet the diadems mortal challenge. A lone raider of the cosmos named Horde managed to get hold of a small fragment of which to become nigh unstoppable. But found that even with his newfound might he himself could not surpass the Crystal keep's trials.
Centuries would pass until the would-be conqueror would stumble upon the then lesser known planet of Earth where he would make contact with the Uncanny X-Men and coerced them with retrieving the ultimate prize hidden within it's confines. Lest the world as they know it come to a grievous end as have countless others in the distant past. One by one the heroic adventurers succumb to their underlying wants and desires while traversing the endless corridors containing their objective. A few of which managing to resist falling into their fantasies made reality only to be fundamentally changed.
To spare his beloved Storm the same fate that befell Ms. Braddock when she tried to rebel against Hoard in her deviant state. Wolverine forced Ororo into her ultimate longing of being a thief in Madripoor while he did his best to hold back their assailant from achieving absolute power.
While faring no better than his other contemporary Psylocke, Logan was summarily slain by the malignant xenoform. But as he lay dying a little of the mutant heroes blood spilled upon the gemstone itself. Supercharging his Healing Factor to the point it could regrow the weathered veteran from his very genetic code as a whole new man. Armed with the power of complete and ultimate knowledge, the resurrected loner dispatches horde by clipping his fragment of the cosmic curiosity. Causing him to rapidly age to dust the very second it is removed. While under the influence of the crystals, James realizes that no one person should ever have this power. For whatever reasons that may. He proves his ultimate mettle by reneging the power given; destroying both the nonpareil alongside it's palace of the impossible.
Unbeknownst to all at the time whom fell to their greatest wishes; when the most aged amongst their number passed it's test. It restored them back to life on Earth; normalized form and all. While the fortification that housed the eye of their quest would be reassembled by its petrified guardians sitting outside it. The Crystal of Ultimate Visions reforming within it's confines to stand as the touchstone to evolutionary progress access once again.
The Crystal of Ultimate Vision grants it's user ultimate understanding of the cosmos and beyond; thus resulting in penultimate capability through a solipsistic effect shared between the diamond and it's possessor.
But said treasure; in it's own way, is sapient and can set up a host of challenges and temptations of the mind, heart and soul of the individuals seeking it. Punishing those whom are found unworthy by transmuting them into its templar overseers while rendering their entire species an evolutionary dead end by forever stunting their racial growth.
With so much as a sliver of the original Crystal; an Individual is bestowed with vast powers but at a weaker degree than what they would have while in possession of the full corundum.
Even still the shard in Hoard's possession was more than enough to give him catastrophic ability levels in his own right.