An influential background character who hasn’t had much visibilty so far is Kerne’s younger sister, Faye – who went to study in the Feywild after their family was split up. There’s been a loose connection between the sisters by way of an enchanted journal, which each has a copy of, and that they can read and reply to each other by writing in it.
It was fairly late in the first year – as the group closed in on a group of Hags who had kidnapped an alchemist – that the DDC realised that Faye was apprenticed to the same Hags, and had been learning their crafts. When they defeated the coven, there was no sign of Faye – and it looked like she had fled with some of their research and materials after chaining up the nearby portal to the Feywild with iron. Removing the chains allowed Faye’s warlock patron – the Winter’s Knight – to emerge into the swamp. He too wanted to know where Faye was – but on learning that Kerne didn’t know anything permitted the group to leave.
Later investigations determined that a block on the group’s memories about their first adventure had been put there through the actions of Faye so that they would not remember Faye’s involvement in an ambush that took place by Morgrave University, and for a while there was a chill in relations between the siblings.
During their most recent adventure, the sisters began sharing knowledge again. Faye confirmed that she was on the run from the Winter’s Knight as the research she had taken pertained to making a drug that the Hags had been creating and planning to spread that made people more susceptible to magics cast by the fae. She was keeping that knowledge hidden to frustrate those plans while the DDC acted against Knight. Cooperating, the siblings were able to create a potion to cure lycanthropy, with Faye passing on the Hag recipe and Kerne interpreting the instructions and ingredients to what was available locally.
What is known is that Faye is Dragonborn, and a warlock sworn to the Winter’s Knight or some other high ranking Fey. She may or may not have taken on Hag-like characteristics as part of her training with the Broken Eye Coven – and quite what her plans and allegiances are remain somewhat nebulous.
As ever, feel free to appropriate character design and concept for your own uses