In the Wugengji, the reason why the generals of the Dark Clan wore iron masks in their death eyes was to protect the Underworld from foreign invasion. In the setting of the story, the Underworld was a peaceful universe country, but it was also threatened by other races. As one of the generals of the Underworld, Death Gaze's duty was to protect the Underworld from foreign invaders and maintain the peace of the universe. However, since the Underworld was strong enough, Death Gaze no longer relied on the iron mask to protect himself. In the story, the iron mask was a weapon that Death Gaze and the other Dark Tribe generals wore together. It symbolized the glory and protection of the Underworld. When the Underworld is threatened, Death's Gaze will pick up the iron mask and fight with other generals to protect the Underworld from foreign invaders.
In the Wugengji, the reason why the people of the Dark Tribe all had Petrification was because of a substance called " Petrifying Oxen " in the blood of the Dark Tribe. This substance could catalyze the blood to coagulate, allowing the Elysium clansmen's bodies to remain solid for a long time. However, this petrifying reagent was limited to a certain extent. When its concentration reached a certain level, the Dark Clan's bodies would also begin to show signs of petrification. Therefore, the Dark Clan would maintain the same form for a long time to avoid petrification.
The reason could be that the creators wanted to give the iron fist comic hero a unique look and make him stand out. Not wearing a mask might emphasize his confidence and raw power.
Maybe it's for protection from something, like dust or germs.
Maybe it's to hide his identity or for some sort of protection.
Perhaps Mang took off his mask to communicate more clearly without any obstruction, or maybe he was following someone's instruction to do so.
Bane wears a mask to control the pain and enhance his strength. It's a key part of his character's identity.
Perhaps the mask is just a fashion choice or it might be related to a specific story or event in the BT21 storyline that gives a reason for Mang to wear it.
Maybe it's for a unique style or to stand out. It could be part of the character's design.
It could be for a more personal reason. Maybe he's going through some internal struggle or self - doubt, and wearing a mask is a way for him to create a new persona, a stronger and more confident version of himself. It's like a shield that allows him to face challenges he might not be able to as the regular Naruto.
In the story, the man in the iron mask was a mysterious prisoner. His identity was kept secret, and he was forced to wear an iron mask all the time to conceal his face.