I'd love a master that screws with terrain in a reality-horror way. Think the portal tech that the Umbra hench has.
A keyword ability "Endless Twisting Hallways; At the end of this model's activation place an Unreal token on a piece of terrain within Aura 6"
A trigger on attacks, "This looks familiar... - Enemy only, place the target in a piece of terrain with an Unreal token."
A free action, "Echoing Laughter - place this model in base contact with a piece of terrain with an Unreal token." With the trigger "It's Coming From Inside the Room - immediately make a melee attack against a model drawing range and LOS from a piece of terrain with an Unreal token."
Grimwell is still the hench, the master is Peggy Rauschenberg. Once a promising architect and painter Peggy was committed to the asylum by her family. Unfortunately her the "treatments" she underwent only made her powers grow and now she has turned the very stones of the asylum to her purpose. Peggy is certain that she is the only sane person left and it is the world that must be cured of its madness.
Her totem is "Patient #5" - a mobile assassin more than a frontline beater. He has Demise (memetic) - attach an Idea upgrade to a model within line of sight before removing this model. The upgrade has two abilities, "Obsession - this model must end its activation in base contact with a piece of terrain with an Unreal token if possible." And, "Ideas Are Bulletproof - when this model is killed summon a Patient #5 model in base contact."