Burn the Witch!: Official policy in the Empire of Chaldreth, though High Priest Gadrath in Daughter of Witches has quietly started spiriting the witches away to serve him instead, burning non-witches in their place if necessary.
Medieval Stasis: Based on various dates given, Shadow Magic, Daughter of Witches, and The Harp of Imach Thyssel take place about 1800 years after Caught in Crystal and 800 years after The Raven Ring. Despite this, all the books exist at around the same technological level.
Nice Job Breaking It Heroes: Quite literally in Caught in Crystal; the destructive black creature was safely trapped until Kayl and her companions broke a chip off its imprisoning cube.
Non-Action Guy: Karvonen of The Raven Ring is in favor of running and hiding as a way to deal with danger. Justified: he's a career cutpurse, and so doesn't want to get caught.
Noodle Incident: In Caught in Crystal, Glyndon smiles in a way that Kayl last saw "just before the incident with the Bridden army officer, the mug of ale, and the dead mouse." She hastily interrupts before anything can happen.
Thou Shalt Not Kill: In Daughter of Witches, healer Mist takes this very seriously; she feels enormous shame over having had to do it once before, despite knowing perfectly well the man was a dangerous monster.
Trust Password: Subverted in The Raven Ring; the villain anticipates one of these and tortures Karvonen into teaching it to him, which he uses to pose as Karvonen and get to Eleret and the ring. There was no such password. Karvonen instead teaches him the Cilhar for "I'm the shapeshifter."
Your Mind Makes It Real: In Daughter of Witches, the death of her parents has left Ranira so terrified of using magic that when she tries, she gives herself psychosomatic burns.
Shadow Magic, Daughter Of Witches, The Harp Of Imach Thyssel, Caught In Crystal, The Raven Ring