The spice

The spice, basically the one in Dune films, could be a new precious material along with redstone.

You can find the spice in sand near desert wells and villages (spicy sand blocks? maybe) and you can obtain from 1 to 2 raw spice powder by using the brush.

Combining raw spice powder with redstone in a spice refiner (similar to the brewing stand) will give you refined spice powder.

Refined spice powder can be used to craft the biome locator, a special compass that let's you find a new rare type of desert biome where there is a lot of spice, maybe new mobs and structures, pretty much like Deep Dark in terms of size.
Maybe there could be a "spice desert" in normal desert and an even rarer variant in badlands, and they have a similar spawn rate to mansions.

This would evaluate again desert biomes that are only used for glass and mineshafts. 
I say "spice" but surely it can have different name to avoid copyright issues.