v399Martian Probe
NPC 399   NPC 399 active
The inactive (searching) and active (detected) sprites.
Type Monster
Sub Type Scout
Rarity Rare
HP 500 Heart
Attack 5 (Touch)
Defense 5
Spawn Time Pwnhammer Icon (Hard Mode)
Sun Moon CharmNew (Anytime)
Spawn Area Surface (Anywhere)
Immune To None

The Martian Probe is a rare Hardmode, post-Golem enemy that is similar in function to the Goblin Scout, in that interacting with it leads to the Martian Madness invasion event starting.

Regardless of where the Probe is encountered, the invasion (like other invasion events) will always take place around the town NPCs/original spawn point.


  • Martian Probes will typically not spawn within the inner two-thirds of the map. This makes the Space layer and the Ocean biome the ideal locations for trying to find them.
  • For faster results, Battle Potions and a Water Candle can be used.
  • Spawn rates are increased during a Blood Moon or Solar Eclipse, as well as increased spawning chance in the space layer.
  • Once a probe is discovered, the event can be triggered by allowing the probe to "scan" the player and fly away. The probe's beam will turn from green to red once it has detected the player.

Update Info


  • Added to the game.