The Congress of the Crowns was formed by Hugh Jones and is comprised of etheral versions of those who have worn a version of the Serpent Crown (or the Cobra Crown) in the past. This includes manifestations of Destiny, Dorma, Krang, Living Laser, Naga, Nelson Rockefeller, Sub-Mariner, Thoth-Amon and Viper. Of the 13 depicted, 3 of them remain unidentified (one could possibly be Duke Villagro) and were removed in a later flashback.
Various retconned wearers of the Crowns were obviously absent including it's creator Atra as well as Gregory Gideon, Justin Hammer, Cornelius Van Lunt, Nighthawk, Owl, Phraug, Sebastian Shaw and Obadiah Stane.
The Congress of the Crowns was created by Mark Gruenwald and Jerry Bingham and first appeared in Marvel Two-in-One #66.
Upon Jones' defeat by the Scarlet Witch, Stingray and Thing, the Congress of the Crowns ceased to exist and as such have not reappeared outside of flashbacks.