Martian Madness

Martian Madness is a Hardmode, post-Golem invasion-style event that includes several alien-themed enemies. It can be triggered after Golem has been defeated.

Martian Madness is triggered when a Martian Probe spawns randomly and detects a player (turning from blue to red), and is then allowed to escape. The event can be prevented by avoiding the Probe, or by destroying it before it can escape; although destroying it is difficult, as it flies off quickly once the detection occurs or the Probe is damaged. Once triggered, the status message "Martians are invading!" appears, and UFOs start flying in the background; though Martian Madness enemies will not actually begin spawning until the player is located at their spawn point.

Tips

 * An effective way to destroy the Martian Saucer is to stay in a base with a curved roof. It will not only protect you from its attack, but also allow you to attack it from base without being harmed. Make sure the walls of the base are thick, otherwise the explosions from the missiles may still be able to harm you.
 * You may want to avoid killing smaller minions to allow more Martian Saucers to spawn during one event. This is easily done by kiting a Saucer away from the spawn point then killing it and coming back for a new one.Alternatively you can set up a teleporter to a faraway point in the world and using it to go away and return fast despawning the enemies until a Martian Saucer spawns among the new wave.
 * It's possible to override it with the Pumpkin Moon, Frost Moon, or other event.
 * If you exit the world just before the probe despawns, the event may not happen when you re-enter the world.
 * Minions can kill a probe before it has the chance to detect you and escape, preventing the event. Minions should be dismissed if the player is trying to cause an invasion to occur.

Trivia

 * The Tesla Turret is based upon the Tesla Coils, invented by Nikola Tesla, which can look similar and are often used to generate arcing electrical discharges ("artificial lightning").
 * The Martian Walker is a reference to the tripod-like Fighting Machines from H.G. Wells' novel The War of the Worlds.