The “Narrator” is the game master role in Silk & Dagger, and it is like that of Eureka: Investigative Urban Fantasy in a lot of ways. The Narrator describes what the PCs can perceive with their five senses, and runs the NPCs, but otherwise absolutely does not interfere with the PCs’ success or failure.
Eureka: Investigative Urban Fantasy encourages rotation of players in and out of the GM role, but it just sorta says it, it doesn’t really do much mechanically to incentivize it beyond that. Silk & Dagger, however, does.
Every time the Spider Goddess gets a Favor Point for pointing out the PCs failing to embody what is expected of their caste, so too does the Narrator. These Favor Points add up to Boons they can be given to the Narrator’s PC next time they rotate out and play a PC.
This separation of duties and power, where the Narrator is not directly in charge of their own reward system, and the Spider Goddess is not directly in charge of their opportunities to gain their rewards, also helps prevent abuse of the positions to the detriment of the game.