He noticed her eyes fall vacant, her attention and focus clearly fading. He takes another sip of his drink. Lips moving behind the cup, soft whispers hidden by the dual drumming. 

That which brushed past her foot continued to move, a solid shadow of pure darkness circling a chair leg and her own. 
It had surrounded both legs, just inches away from touching her as it raised up the back of her chair. 
With one word it would tighten. 

He simply watched and waited, seeing what she would do before he made his move.