Mummification allows Hoyo to manipulate the red bandages he is wrapped in to ensnare inanimate objects that gets caught in them and turning them into humanoid red mummies that he can control at will and make them fight for him. Although the limit number is unknown, Hoyo can control dozens of mummies at the same time.
His Quirk only works on inanimate objects, so he cannot control living beings directly, but he still can indirectly control them by manipulating clothing and objects that people may possess with his bandages, and in this way, use them to attack and provide himself with human shields.
The bandages can be broken with enough force, causing Hoyo to lose control of anything that he caught.
Although he can move people around with his bandages through the clothes and objects they wear, Hoyo cannot prevent the captured people from trying to free themselves, like when Katsuki sacrificed one of his Grenadier Bracers to free himself from the bandages that wrapped him.
If Hoyo is knocked out, the Quirk stops working.