The Ouroboros is the ancient symbol of a serpent biting it’s own tail. I’ve read it described as a symbol for the balance of creation/destruction, a representation of unity, of eternity, of things moving in cycles and more. The symbol has been used by many cultures dating back to the Hongshan period in China, 4700-2200 BC.

In Heathenry the Midgard Serpent, Jörmungandr, was thrown into the ocean surrounding the world by Odin, and it grew and grew until it began to devour its own tail. Some of the kennings used for Jörmungandr include surrounding saithe of all lands (saithe being explained as a type of fish), girdler of all lands, saithe-fish of earth, necklace of the earth, earth’s stiff neck string and fish of the sea bottom (all from the Poetic Edda edited by Paul Acker and Carolyne Larrington). None of these imply that Jörmungandr is an active threat while lying on the sea bed. It’s only when it rises up out of the sea at Ragnarök, away from its place in the scheme of things, no longer devouring it's own tail, that it becomes a force of destruction.

Are there any other myths where an Ouroboros comes undone, so to speak? Any dragon people have any insights?

Syn

it was on red dwarf lister was found with a box with our rob or ross written on the side so the people who found him thought his parents couldnt decide on a name for him. then when he had a son he put him in a box with ouroboros on the side and took him back into the past to be found by his own parents = he was his son and his son grew up to have his father.
not really mystical i know but fun bit of tv trivia on the subject