"A bit of an experiment," Antorel explains, "This is my latest attempt." He reaches into his cloak and takes out a glass vial of grey powder. His sister's eyes get wide and she looks at Yarl, then back at her brother. Again he says something to her in their shared language. "There is a counter-agent of course, I'd be a fool otherwise. Only enough right now for me and sister dearest, in case of exposure." Looking Yarl in the eye, he tucks the powder back in his cloak. The way he's talking it sounds like he's done 'experiments' like this before.