“Adventurers, do for me these deeds and I will make sure your time is compensated” says Atour the Azer.
Atour was summoned to the Material plane by a devil, made to work on weapons for a goblinoid horde. The horde was defeated but the magic the devil used on him daily for years have anchored him to this plane. When he gained his freedom, he didn’t mind it. It was great being able to do as he wanted and Material was “alright.” More importantly, he had a mission: Revenge.
He picked 3 targets.
Gartoush the Hobgoblin, the one that consulted the devil on what weaponry to use, the one who suggested summoning an Azer. He bailed out after getting his payment and is probably out there consulting some army or enjoying the gold he earned. Atour wants to take all his belongings.
Gnosh the Grim, the “quality control”, a duergar that tested the quality of Atour’s weapons by “testing them” on the Azer. If he didn’t do enough damage, he would hit again, and force the Azer to remake the weapon, even though the reason was always because Gnosh was wielding a weapon he had no idea how to. Atour wants to kill him.
Senj the Oni, who the devil asked to train some of the goblinoids. Atour wants to thank him, for Senj was respectful and appreciated the sword the Azer forged for him. In fact, he means to give Gartoush’s belongings to Senj, along with Gnosh’s right eye, for one time Senj witnessed Gnosh’s cruelty, he cut the duergar’s face, wounding his right eye permanently.
Once these targets are done, he wants to take the devil down if possible, but he doesn’t know its name. Should he find more, what Atour wants is to demote the devil all the way down to a lemure. Last time they met, he was a War Devil.
Atour can be plugged in to pretty much any adventure. The three targets don’t need to be targeted one after the other. It makes mechanical sense that they are increasingly stronger enemies and story sense that Atour tracks them down in between. Atour can provide info for the party to deal with them or join the hunt himself.
Atour can also be an ally, crafting decent items for good prices, maybe crafting something unique at the end of the quest. He can be one that takes the “forger” role in any quests where a unique one is needed and can also make a good companion should the party build a base.
A very obvious hook is the players playing a part in the goblionid army’s downfall. And of course, the one who summoned the Azer could be a wizard or some other entity, same with the three targets.