When I see all the children of Discord and Cosmos in different art pages, it gave me something to see that Princess Eris is the only one of the 3 who does not have children of any couple, so I set to create a daughter, Ath, by the name of one of Eris' daughters in Greek mythology such as Lethe.
Who was the lucky father? It's something that nobody would wonder about how obvious it is, Tirek, about things like humiliating Discord, having been a prince in his past, almost conquering all of Equestria and his muscles; all those generated great attraction in the feathered draconequus.
Meanwhile, Tirek had fallen in love with Eris's malice and power, in addition to his dislike of Discord, and beyond passion, he also saw it as a strategy to woo a draconequus to have a great power in their descendants to resurface their empire to become the most powerful in the universe. It was Eris or Cosmos but the last one was too obsessed with Discord, so, Eris was the better option.
How is their daughter? She is a teenager who moves away from her parents' wishes to be a queen of chaos since she is really not interested, what she loves is to create stone statues with the thousands of rocks she has in the cave that they live.
She doesn't have a grudge with her uncle's family to such an extent that she can get along with her cousin but prefers to avoid family reunions because of her father's constant fights with her uncle.
Another thing she likes to do is scare people with long mazes where she uses her statues as creatures that chase him, the only thing her parents are really proud of.