I have actually thought about this in sufficient detail to outline a series.
My pitch is simple: Undermountain.
Most fantasy stories focus on epic quests where the fate of the world hangs in the balance. In this show, we instead focus on working-class adventurers. They don't go into Undermountain because they need to save the world, but because they need to feed their eight kids, pay off their gambling debts to a criminal syndicate, or buy their way into the nobility. These are relatable, everyday heroes and anti-heroes.
Undermountain itself has a distinct Old School vibe. It's scary and suspenseful. Terrifying monsters, glittering treasure, strange magic, and endless corridors of choking darkness. Death is swift and arbitrary. But not always final.
The Yawning Portal is neutral territory where enemies and allies alike mix and mingle, talk trash, and even romance each other.