Menderbug

Menderbug is an enemy in Hollow Knight. He can be found repairing the sign at the bottom of the well in the Forgotten Crossroads.

Behaviour and Tactics Menderbug has a 2% chance to spawn at the entrance of Forgotten Crossroads right below Dirtmouth. To spawn, the following conditions must be met:
 * The sign at the entrance must be destroyed
 * The Knight must leave and re-enter the room

Upon seeing the Knight, Menderbug quickly flies away and leaves the room.

To kill Menderbug, enter the Forgotten Crossroads from Dirtmouth using the Desolate Dive/Descending Dark Spell. This destroys the sign upon landing and, if he has spawned, also kills Menderbug. He can also be seen when entering the room through the east and west doors of the Forgotten Crossroads, and can be killed with Vengeful Spirit/Shade Soul. This requires less soul and doesn’t require killing Soul Master to get Desolate Dive, which means he can be killed early in the game. However, this method takes significantly more time and makes it easier to fail to kill Menderbug. One of the easiest ways to catch him is in the late game after acquiring Kingsoul and/or Salubra's Blessing to refill SOUL easily.

Menderbug's Diary After killing Menderbug, his house is unlocked. The house can be found in the same village where Sly is first found infected.

Location Menderbug is located beneath the well in the Forgotten Crossroads.

Trivia
 * There is an unused key found in the game files named Mender_Key. It is implied in cut text that Menderbug would drop this unused key called an "Odd Key" that would probably then allow access into his house.
 * Killing Menderbug is not needed in order to acquire the Hunter's Mark.
 * Menderbug cannot be read by the Dream Nail.
 * Upon death, Menderbug emits an Infection cloud. It is unclear if this is intentional or an oversight.
 * The sign at the entrance of the Forgotten Crossroads remains broken after Menderbug is killed.
 * Menderbug still spawns in the Infected Crossroads.

References

Починжук Insecto_reparador Majsterobak Fixeur Riparatore