The Dragonslayers become the Favored Few
: A group of (friendly) rival adventurers composed from the players in another GM's campaign. Led by Cernan the Wizard and Zosime the Rogue - they have a similar group of characters to Our Party.
In their own campaign, "Faerun-ers" (WorldAnvil link) they go by the "Favored Few" - but as the story for Our Party began, they were known as The Dragonslayers.
Always overshadowing Our Party, this group's successes showed the world was not centered solely on our own player characters. (Read more in "Early Deeds of the Dragonslayers").
However, this hubris on the part of the rivals caught up with them, as the flaunting of all that wealth - and the raiding of Castle Naerytar brought a dragon-backed raid on the poor town of Phandalin (standing in for "Greenest" in Hoard of the Dragon Queen).
After the town's destruction, The Dragonslayers down-played his name and stayed on to host the townspeople in the Tresendar Manor they were restoring - and work at rebuilding Phandalin before returning to more adventures.
But after the events of Phandalin in Flames, shamed and seeking to lift the name that drew such unfortunate attention - they adopted the name the Favored Few.