Mad Endo is an endoskeleton boss and one of the several bosses encountered in FNaF World. He guards yellow and red chests in Deep-Metal Mine. He also guards a red chest in a hidden part of Choppy's Woods.
Mad Endo's appearance is almost identical to Endo-02's appearance, minus the skeleton-like head and the strange two-toed feet. Its body seems to be merged together, giving it a strange look. It is noticeable that if one looks closely, it has sharp claws. Overclock and Gold Endo have them as well, due to being just a powered-up version with nothing changing in appearance and a recolor, respectively.
Basic blue tackle attack
Deals medium damage to a single party member.
Decreases the attack power of all party members and negates the effects of Gift Boxes and Neon Wall.
However, one of them appears in Choppy's Woods, only to guard the chest that holds the Pizza: Fury chip.
Mad Endo is one of the five bosses that are considered optional bosses, since the player doesn't need to defeat it to complete the story. The other four being Auto Chipper, Eyesore, Seagoon and Gold Endo.
Mad Endo is the only boss that has the Gloom attack.