Oh wow, I love this. That sex scene is one of the most sensual passages I've ever read. I didn't like Muriel one bit in canon, but you've made such a fascinating and interesting character of her (just like the title says!), and I adore your Ollivander and his levelheadedness, even in the face of pain.
Just a few of the many beautiful lines:
He is a keen studier of people, an observer of social currents and the tides of power.
And somehow – some clever Slytherin trick of tone and smile, probably – he suddenly feels like he has not been playing whatever game they began at dinner, but is instead a piece in it, and she has just manoeuvred him into exactly the position she wanted.
Magic twists in the air, wild, and snuffs the candle out before it fades.