Does anyone remember that Satanic temple/altar (with a statue of a demon goddess attached to the roof) Dark Willow raised on a bluff outside Sunnydale in the season finale? Do you also remember the color of the fire Willow was channeling into the effigy?

That was a centuries old shrine dedicated to the demon goddess, Proserpexa, to whom Willow is bound because of invoking her name, "awakening" her basically after centuries of torpor. The lamia-like entity visits her during her walkabout post-Sunnydale's destruction AND in a vision when Willow tried to bring Buffy back from the future.