Kuroi Tsubasa No Tenshi

The most recurring monster of the franchise, he has had six appearances across various media. It is tradition for this character to be redeemed and fight alongside the heroes sooner or later.


Raferou

World : Sekai
Source : The Elrik Saga


Angelus

World : Sekai
Source : The Girl Who Deals With Monsters


Zaha

World : Tengai (anime)
Source : Rokumon Tengai Mon Colle Knights


Gren

World : Tengai (manga)
Source : Mon Colle Knights manga.


Flame

World : Sekai
Source : The Maria Saga


??

World : Sekai
Source : The promotional video


Deonea

Continuity : Sekai
Source : Dragonmaster Anya

Also called the Fallen Angel of Sylaster (a kingdom).