The Martian Drone is a Hardmode, post-Golem flying enemy that spawns during the Martian Madnessevent. Upon spawning, it flies diagonally up from a bottom corner of the screen, moving through blocks. If not destroyed, it stops once it reaches a point just above the player, then spins and explodes into spark particles that fall and linger on the ground, which will damage players or NPCs that touch them.
If the player is inside a tunnel, the drone will stop pursuing and hovering on the player's head as long as the player stays in tunnel. The same strategy applies to dealing with Corites.