Is there an equivalent of the “Underworld” in Marvel?

Does an “underworld” concept exist in Marvel? Could we get a sequel series with Agatha and Teen visiting the land of the dead and visiting or resurrecting members of the Coven, Nicky, Tommy, Wanda, Sparky, etc? Can Agatha herself be resurrected? Does Rio/Death lord over the land on the other side of the “green door” that she and Alice walked through? I’d also be curious to hear what Rio/Death thinks of the snap or the blip and all those people coming back, etc. This show was like the very beginning stages of peeling back the layers of the onion and I just want more. I feel like there is such untapped potential for more. Loved it so much!