Lazotep

Lazotep is a magical blue mineral exclusively found on the world of Amonkhet, which interacts with necromancy in strange and powerful ways. It was the main reason Bolas turned his attention to Amonkhet.

Description
Originally, the people of Amonkhet used Lazotep to seal the wandering dead in tombs. The mineral was mined extensively in the Broken Lands by servant mummies, and used in the creation of cartouches, indicating its role in control magic and the preservation of life force and a person's deeds in life. Ultimately, lazotep was also sneaked out in the funerary barges of the worthy dead, where it was used in the Necropolis to create Nicol Bolas' eternal army, resilient undead coated with layers of the material. He then transferred this Dreadhorde to Ravnica by way of the Planar Bridge which could only transport non-living matter.

Trivia
Lazotep is based on Lapis Lazuli, a real-world precious stone that was highly valued by ancient Egyptians, for its aesthetic and supposed magical qualities. Their chief god, Ra, was believed to have hair made of lapis lazuli. The name may also be a portmanteau the names Lazarus and Imhotep.