天魔、素兎、蟲人、八雲
博霊、魔神、空孤、童子 etc..半分ネタですが・・

以下、少々長いですが求聞史記より要約抜粋

「龍。手と角が付いた蛇のような姿をしていて、太さは
樹齢数千年の大木を遥かに上回り、長さは空を覆う程だと
言われている」

「最後に龍が現れたのは、博霊大結界を貼った時のことである。
天が雷鳴と豪雨に包まれ、暫くの間、昼も光が差さない闇の
世界に陥った。」

「妖怪の賢者達は、自分の存在を賭けて龍に永遠の平和を誓うと
水は瞬く間に引き、空は割れ、地上は光を取り戻したと言われる」

Tenma, the White Rabbit, an insect person, Yakumo
Hakurei, the God of Makai, Kuuko, Douji, etc.. Only like half of them are official, but..

This is a little long but it's summarized from Perfect Memento.

"Dragons. They're said to look like snakes with horns and hands whose girth exceeds those of trees that have lived thousands of years, and are long enough to cover the sky."

"The last time a dragon was seen was when the Hakurei Border was cast. The skies were covered in lightning and rain, and for a short while, the world was cast into darkness."

"When the sages of the youkai swore an oath of peace to the dragon on their own lives, in an instant the rain stopped, the skies parted, and light was returned to the earth."