Form No. 1 - a large, brown Yin-Yang Orb, with red markings. Form No. 2 - a female priestess (?) in red robes with long, flowing red hair, horns and glowing red eyes. Form No. 3 - a male priest (?) in white and blue robes with glowing red eyes. Has a slight resemblence to a feudal souhei.
Shingyoku appears to prevent Reimu from entering the gateway, or perhaps to test her resolve. Next-to-nothing is known about this enemy, as it does not exchange dialog with Reimu and has no official profile. Judging from its appearance, Shingyoku is likely somehow related to the Hakurei Shrine's past.
Since Shingyoku has two forms, but one is male and the other female, it is unknown which is it's true gender.