In the original, the challenge gate is a simple rotating model emitting the shrine sound. A floating quad rotates around the center, emitting a simple particle effect. The quad is textured with the sketch-art of a Sharpclaw. The texture provided has been corrected as the original engine would, however I've also provided the original texture which the engine uses adds onto a flat color and extracts the alpha.

The edges are faded by multiplying the red channel of the vertex colors into the alpha. Raise the alpha by a decimal exponent to increase the visibility.