I am wondering if Mab’s rule against spilling blood at Arctis Tor is not simple court protocol. Here is the relevant scene - from Cold Days (hardback ed.) at 59:
A large ruby droplet fell from her lip and hung in the air, shining and perfect, and there for half of forever. Then it finally splashed down onto the icy floor.
There was a shrieking hiss as the blood hit the supernatural ice, a sound somewhere between a hot skillet and a high-pressure industrial accident. The ice beneath the drop of blood shattered, as if the droplet had been unimaginably heavy, and a web of dark cracks shot out for fifty feet in every direction.
The music stopped. The Redcap froze. So did everyone else.
Mab rose out of her chair, and somehow in that instant of action she crossed the distance from her high seat, as though the simple act of standing up were what propelled her to the space nearby. As she came, the pallid finery of her dress darkened to a raven black, as if the air had contained a fine mist of ink. Her hair darkened as well to the same color and her eyes turned entirely black, sclera and all, as did her nails. The skin seemed to cling harder to her bones, making her beautiful features gaunt and terrible.
At first I thought the rule against bloodshed just dealt with the rules of hospitality. As host, Mab likely had to extend safety to her guests, so a rule against fighting was necessary to allow enemies to attend the same gathering. I thought Mab’s reaction was anger at having her rule thwarted. Neither the rule nor her reaction would have anything to do with Mab’s personal tastes; I doubt very much that she would be squeamish about a fight to the death at her party.
But if the rule is just about rules of hospitality, why not decree “no fighting”? Why the specific rule against blood? I think the blood is important in some specific way. Note the way even the ice reacted to the touch of blood—almost like some sort of shrieking alarm. And similar to the way the doors at Artis Tor reacted to Charity’s iron ax in Proven Guilty. It seems that Arctis Tor reacted to the blood as a poison the same way it did to iron.
Likewise, I don’t think Mab’s reaction to the blood was out of anger; I think it was involuntary. As mad as she was in SmF when she was talking to Harry at the hospital and made his eyes freeze, she did not turn black and have some sort of strain on her that made her skin stretch over her bones and her features gaunt. Though to a lesser degree, this description echoes what Mab looked like in Changes after she spent months, using all her strength to keep Harry alive at a terrible cost to herself. Therefore, in Cold Days, I think the blood falling on the floor caused some sort of involuntary physical reaction in Mab. I am imagining it as something like an immune response; she was protecting herself against the blood.
Finally, the way Mab responded, by darkening to a black color as if pulling a fine mist of black ink out of the air sounds reminiscent of a couple different scenes from the series. It sounds like the way the Black Staff pulled out of Ebeneazer black tendrils of what I assume was taint from performing black magic. It also echoes the black inky mist like tendrils of the mordite mist-fiend, an outsider.
So….is it possible that Mab’s reaction was a built-in autoimmune response to the possibility of a contagion? Is it possible that Nemesis is a blood born contagion?