>>283384086
>For reasons unknown, posters and merch switched it to these characters. It roughly means "By heaven's command, follow and protect life."
>勅命随身保命
More precisely, the characters are "勅令陏身保命," which roughly means "carry this to protect your life." It is a protective spell against evil. The first two characters are a common phrase in Taoist incantations and do not necessarily represent an imperial command. Using this amulet as an accessory for Chinese zombies is a uniquely Japanese cultural practice based on a misunderstanding. Its origins have already been explained by this anon.