Kagol was a minor recurring demon first seen in the original Devilman manga.
Kagol was a humanoid demon, he had markings across most of his body long sharpened teeth and a single cyclopian eye.
Ryo Asuka explained the origins of the demon race to his best friend Akira Fudo. A while later in current time Kagol is one of the demons sent by Zennon to assist Sirene after she was critically injured by Devilman, he attempts to attack Akira but has his face sliced through with his claws presumably killing Kagol.
Kagol briefly returns as a part of Vlava's army seen at the forefront of a group shot.