The being known as the Adjudicator was created in an alternate universe by a race of beings known only as the Overseers. These beings, of apparently omnipotent power, arrogantly took a citizen of their universe whom they considered to be insane and a nuisance, and granted him the power to serve as judge, jury and executioner of all other universes, which they felt were insignificant.
The Adjudicator has cosmic power on an impressive scale, and among the feats of which he is capable are: teleporting across dimensions at will, transforming himself into replicas of a given world's dominant Doomsday scenario (such as Earth's Four Horsemen of the Apocalypse), and completely obliterating any universe which he finds unworthy. As if these things were not horrifying enough, the Adjudicator's own arrogance and insanity causes him to find all of the universes he encounters to be unworthy…and so he has blithely destroyed every one that he has entered.
Ultimately, in the months preceding the Crisis on Infinite Earths, the Adjudicator came to the dimensional crossroads leading to the Multiverse, and prepared to judge the various dimensions within it as harshly as he had all others. His presence was noted by the super-heroes of the various Earths within the Multiverse, and the female heroes in particular; the vast majority of these heroines joined forces with the Wonder Woman of Earth-One to combat the Adjudicator.
At first, it appeared that despite the impressive power level of the assembled heroines, the Adjudicator would succeed in his goal of destroying the entire Multiverse. However, in the end, Wonder Woman was able to ensnare the Adjudicator in her magic lasso long enough to cause him to confess who had given him his mission of judgment, and remembering the Overseers also created a psychic link that allowed the Overseers to find him and render their own judgment upon him. Feeling that he had overstepped his bounds, the Overseers removed the Adjudicator from the Multiverse and returned him to their own dimension. He has not been seen since then, and whether or not he will ever return remains to be seen. Numerous questions remain regarding the motives of the Overseers in all of this, but until either the Adjudicator or the Overseers are seen again, those questions will remain unanswered.