Mongo in the 1980 movie became the world of The Big O
After Flash saved Mongo and Earth, the Mongans were ruled over by Prince Barrin peaceably. But Prince Barrin abandoned Mongo to become a certain secret agent. Then Mongo descended into chaos. The Mongans became darker and more mundane until their entire way of life became dreary. All that remained was the hope of a great hero to save them and Flash Gordon's theme music - which the theme music of The Big O sounds suspiciously like. The identity of the ring-taker.
In the stinger, a black gloved hand reaches into frame and picks up the ring. While it could have been any of dozens of guests, there were three speaking characters present with black opera-style gloves: Dale, Aura, and Zogi the Priest. Any of these three people would be likely to pick it up - the Priest Zogi out of habit/loyalty; Aura because it belongs to her/her family, Dale because (a) she was right there and (b) it was her engagement ring after all. But there was one more person with a vested interest in the ring who wore black gloves and was present at the wedding - Klytus. When Ajax is approaching Vultan's Kingdom, the captain awakens Klytus to ask for mission advice; Klytus is on a horizontal slate in a closet, which rotates up into a ready position. Klytus does not respond until the slate is vertical, speaks, then asks to be woken when they arrive. If Klytus is really the Chess Master they make him out to be - and there's no evidence to show he isn't - would he really risk his neck by walking with a light escort into Vultan's hall? Klytus was only able to keep Vultan in line in the Emperor's presence by directly threatening his daughter. He knows Vultan is too much of fighter to be cowed in his own kingdom; facing him alone would be (and was) suicide. So he sends a simulacrum to die gorily, and confirm Barin and Vultan's treachery. This also allows him to step into the background and await the outcome of the Barin/Gordon/Vultan rebellion. During the confrontation with Gordon, notice that Ming never mentions Klytus' death. Klytus! The man is so powerful he can torture the Emperor of the Universe's daughter on suspicion of treason, and Ming doesn't notice or care that he's dead? Not to mention he has been promised Aura to wed ("...marry her to someone worthy of her treacherous nature.") When his lover Kala sends War Rocket Ajax to bring back Gordon's BahDay, Klytus is still hidden on board. The 'Ajax' crew are the only other ones who know this, and they all are killed fighting the Hawkmen. After the crash, Klytus was in a perfect position to watch the entire drama with Ming play out unnoticed, and then, while the victors were dancing and celebrating, swoop down upon the forgotten ring, rescuing his friend (well ok but you know what I mean), mentor, liege, and father-in-law, not to mention securing his position for a long time to come.