I have a former military officer from a powerful empire searching to put a stop to the evil plan of a group of dark elves. They are trafficking people to their homeland to sacrifice to their god/patron. He is partnered with a woman who's father in law is a dark elf, a paladin half-elf, a tabaxi whom he hired, and a female dark elf that is attempting to help him bring down this group. They go to the woman's father in law and he will point them in the direction of a being capable of stopping the dark elves. But I don't know what to fill the cracks with. What can I put in between the story to help make it full and a good read?
If this is the story it doesn't feel personal for the characters,why would they (except for the Tabaxi) do what they do? So i guess that would be the focus, explaining why they are doing what they do without literally spelling it out.
Take your former officer, why did he lose or leave his position? Was he tired of the inaction of the empire towards the threat? Did he do things he is less then proud of while serving the empire? And along the way you can show it by showing off the failures of the empire to stopping the threat and how he acts on it (and gets side tracked by trying to fix these failures himself).