After a contingent from Atlantia, the kingdom of merponies, shows up near Seaaddle with armed and stone faced aquatic warriors demanding the capture of the ones who have terrorized many merfolk in the area. Twilight is summoned to the west coast in hopes of adverting a clash with the Royal Guard when no pony knows whose responsible, she searches the beaches and wilderness until she comes across a pod of Sirens by luck alone.
Nearly losing them as they attempted to flee, she inadvertently angers the Matriarch of the few who after intense talks is made to realize the danger she's put her family in. Having defended the coast from harmless merponies out of desperation for territory, the threat of an army of well armed Atlantia warriors ceases her embargo over the zone. Twilight manages to earn a sliver of friendship when the Matriarch confirms who she is, the one who stopped Discord and Tirek with her friends. Those who'd threaten their audience with chaos and pitiful dregs of emotion from stolen magic, too tired and drained to provide negative emotions a few mothers needed for their young pups.
Crisis averted, the pod unfortunately seeks a new hidden home but vows to Twilight that if she ever needed her help all she had to do was call from the shores. When asked about ever knowing the trio of The Dazzlings, there was a terse response of a growl that in itself was the sirens answer.
***
Been reediting The Siren's Remorse fanfic, so if you liked the material give the story a read? In a way the piece does fit into the story though whether it will have any place in later chapters is unknown.
https://www.fimfiction.net/story/328044/the-sirens-remorse