Dragon Slayer 4(Legacy of the Wizard) Gers

ドラゴンスレイヤー4 ドラスレファミリー キャラクター図鑑

Gers / ゲルス

Official illust
Manual / Kadokawa guidebook

JICC guidebook

Basic info

Kadokawa guidebook
They were a plasma fireball that existed in the mountainous region of northern Pakistan and was sometimes described as a Zoroastrian deities. The three of them usually act together, flying at breakneck speed through the air at will.
JICC guidebook
It is a monster that appears to be a combination of three burning flames. Some of them are flying at great speed.