the way the catalyst (or at least an important piece in getting the plot to start and continue) for the plots in all the Faerie books is a Faerie falling/being in love
Roiben being in love with Kaye is why she didn't die at the Tithe, why she was able to bring down the Court of Flowers, it's why he trusted and listened to her advice even when he had no real reason to trust her
Kaye being in love with Roiben is why she wants to help him so much, why she declares herself to him and solves his impossible quest, and why she brings down the Court of Flowers to save him
Ravus being in love with Val is the only reason she gets help with her addiction and is kept safe from other Fae
Jack being in love with Hazel is the whole reason she goes to the moonlight revel and gets enough info to save Fairfield
Severin being in love with Ben is the whole reason Ben and Hazel have any interactions with him and get his help to fight the Alderking
Madoc being in love with Eva is the reason he asks her to come back years and years later and kills her when she refuses, the reason why he took Jude and Taryn to Elfhame
Cardan being in love with Jude is vitally important, most of his decisions are made because he loves her and trusts her
Vivi being in love with Heather is the reason she learns to respect and understand humans more than her sisters ever did, the reason she's willing to start all the way over with Heather just to be with her
Oak being in love with Wren is the reason he continues to trust and help her when she literally tries to kill him and locks him, why he risks his sister's trust and the High Court never letting him return to help her
Wren being in love with Oak is the reason she tried so hard to help him, the reason she makes such confusing decisions, she's confused, she loves him so much but she's supposed to let him die
there are tons of Fae scattered throughout the books who are trapped in servitude or prison because they had to save their lover, at any cost
(ofc familial and platonic love also matter and affect the Fae but in an entirely different way)
and the way this all connects back to that line in either Valiant or Ironside saying that Faerie do everything with their whole self, love and hatred, they can love and hate for centuries, promises will never be forgotten and heartbreak hurts deeply
a Faerie loves so deeply in this incredibly genuine way and when a Faerie is in love it thoroughly influences their actions
they tell the truth even in ways they may be unaware of (or deeply ashamed of)
(also also also the way most of these pairings are Fae being in love with mortals is soooo meaningful because like despite many of these characters hatred or distaste for mortals and the Fae's general dislike of mortals they can't help when they fall in love with one as naturally as if they were any other Faerie)