Necromancers and Red Desert Temples.

A new biome, called the Sunburnt Desert, simply a red variant of the desert, with quicksand pockets. Quicksand works like powdered snow.

The Sunburnt Desert Temple houses a boss chamber, with the Necromancer boss. They summon armies of Husks and Hollows (a desert skeleton). They drop a Necromancer staff that can shoot blasts, doing extreme damage to anything alive, but healing undead mobs.

The Necromancer lies in a Sarcophagus, but will only awake if the player opens or destroys anything in the surrounding room. The Sarcophagus can be picked up with a Silk Touch pickaxe and can be used as a bed for skipping the day.

The Chest loot would consist of Buried Fortune Maps, among other things. You can find the Heart of the Desert from these Buried Fortunes. When crafted with 8 Kaurna Tentacles (Sand Octopus), it will create a Sandboni. The Sandboni needs direct sunlight and can be powered by Chiseled Sandstone, just like a Conduit with Prismarine. The Sandboni sets all undead mobs on fire, regardless of the time of day. It can even burn Husks and Hollows. The Husks sometimes carry and drop Kaurna Tentacles.