Back in Dead Beat I believe it was, Harry told Morgan that he believed that the Red Court were
acting as cat's paws for someone else. Possible answers were the Black Council, Outsiders, etc.
Then after Changes, the Fomor seemed to come out of nowhere and the conventional wisdom was
because the Red Court kept them in check, removing the Red Court, removed the cork in the bottle so to speak.
I finished Bombshells last night, and there was a curious line about the bomb that was planted at the party by the Fomor. Lord Froggy says to Listen
Listen bowed his head. "How efficacious do you anticipate your gift to be?"
"The one I made for the Red Court in the Congo was deadly enough," Lord Froggy said, a smug tone in his voice.
My heart pounded even harder. During the war with the White Council, the Red Court had used some kind of nerve gas on a hospital tending wounded wizards.
You don't make nerve gas bombs for someone who is an enemy, or even someone keeping you in check. You make them for a partner, an ally, for someone you want to do the dirty work for you.
So Harry was right is appears, the Red Court was a cat's paw, for the Fomor, not the Black Court or Outsiders. What is more, the Red Court were being used as one huge diversion, while the Fomor quietly, stealthily built up their forces under the lake and elsewhere. Not unlike the events when Harry's duel with Count Oretega set off the war before the Reds were fully ready to fight, as Shiro said. Perhaps the events in Changes, Harry killing off the Red Court forced the Fomor to come out into the open before they were really ready? It looks dire for Battleground, but there is a glimmer of hope there as well, the Fomor could be moving before they are really ready to move.
The other part of this is the reason Lord Froggy had a bomb planted at the party that was supposed to celebrate the Fomor/Svartalf alliance or non aggression pact,was to get revenge on Marcone. Lord Froggy is very specific, he wants confirmation that the Baron was there. Then says he will pay for what he did to his brother. Which brings us to the next point, Molly breaks it up and Lord Froggy nearly kills her before Etri shows up and saves her. Lord Froggy is dealt with, however Listen and his Turtle necked cohorts are allowed to go. Molly objects, but Etri says they have no quarrel with the Turtlenecks because they got Lord Froggy.. He was the one who violated their guest law, "you go after the hand that uses the hammer, not the hammer." We also find out that though supposedly Thomas was acting as an agent or spy for the White Court, the Svartalves considered him pretty harmless punishing him with lots of sex apparently, then he was free to go.
Which brings us to the events in Peace Talks. The original bomb was planted by Lord Froggy to get revenge against Marcone. The plan was thwarted by Molly and Atri, though Lord Froggy was dealt with, Listen and company were let go to fight another day. Or seek revenge, in Peace Talks it was a bomb that went off and nearly killed Etri. The Fomor were attempting to get revenge against Etri for what he did to Lord Froggy. Poor Thomas just happened to be there at the time partying, but since he had been an agent in the past, he gets the blame for it. Which also worked to their advantage not just as a diversion, but because of the events in Bombshells plausible deniability, easy to just point the finger at Thomas.