The demon rune is an item in the 2016 Doom reboot which occurs only during multiplayer game play. It appears as a floating red pentagram with a set spawn point. It transforms a player into a powerful demon when touched.
When taken, the player who obtains the demon rune will be transformed into a revenant, able to fly using a jetpack and fire homing missiles at opponents. This transformation lasts for a total of 60 seconds, after which the player will revert to his or her human form if they have survived. It is possible for other players to kill the player who has become the demon, and doing so will cause the demon rune to drop, where it can be collected by any other player to begin another full 60 seconds of mayhem.
The demon rune will otherwise eventually respawn, with its reappearance announced verbally to all players in the game 15 seconds beforehand with the message, "Demon rune spawning in 15 seconds."