Burned into the wall of the White Dove theater...

[Scott]

Bride of metal, bride of bone
One of circuits, the other a throne
Two girls were begot, bloody ivory’s scheme
All a part of her twisted dream
One of three mothers to steer destiny
A great danger as she lacks empathy.
When the two daughters of Dionysus meet
They shall become Janus complete
Slay the enemy with a great sword
Lest he loose his endless hoard
Through the twins lies Yog-Sothoth
Dimensions and worlds felled in a swath
Or save the children so interdependent
Gain knowledge of the transcendent

[Fantômas]

What I think it means -

Bride of metal, bride of bone
One of circuits, the other a throne - Maddie and Princess Dani
Two girls were begot, bloody ivory’s scheme - The babys that were born. Bloody ivory = white??. This could also refer to Doctor Morton (He is running San Francisco.=> Saint Francis => Stigmata on a holy man=> bloody ivory)
All a part of her twisted dream
One of three mothers to steer destiny - Maddie, Mildred & White are the three mothers?
A great danger as she lacks empathy.
Sheila Vitus: When the two daughters of Dionysus meet - Dionysus = Alex & Mildred. Not sure what is meant by "Sheila Vitus:". Latin/Elvish for something or someone?
They shall become Janus complete - Mildred has stated that this has occurred - heroiccthulhu.proboards.com/thread/4449/daughter-possibly-end-world
Slay the enemy with a great sword - Alex has this sword. Don't know if anyone else also has it. Zog being the enemy
Lest he loose his endless hoard - If this was horde, I would think it refers to the Blight Brotherhood. As it is hoard, perhaps gold? And this would ruin the various realms economies?
Through the twins lies Yog-Sothoth - Interesting, on of my earliest theories about what was going on involved Yog-Sothoth
Dimensions and worlds felled in a swath
Sheila Vitus: Or save the children so interdependent
Gain knowledge of the transcendent

[Scott]

"Sheila Vitus:" was a copy paste error. Ignore that. Fixed OP.