The Shield-Drone Beacon is a Hardmode Support Staff that is dropped by Martian Officers during the Martian Madness event. It works similarly to a summon item; it spawns a Shield Drone which stays near the player's shoulder and rapidly shields nearby allies with the Barrier buff, providing them with additional temporary maximum life that stacks with successive shields up to a limit and decays over time. Shield Drones are invincible and follow the player for an unlimited amount of time, unless the player dies, summons a replacement shoulder guardian, or cancels the buff.
Shield Drones do not follow the typical minion summon limit, so they can be summoned without affecting it. However, only one shoulder guardian can be active at a time, so you cannot summon multiple Shield Drones or any Lil' Cherubs or Lil' Devils at once while it is active.
Like all healing items, it benefits from any additional healing effects and cannot receive a Modifier.