"Okay, if you're sure. Just, uh... think of nice things, I guess."

And Taako holds up his casting glaive, aiming the tip of the blade towards Syrlya's arm.

"Oh, and, uh, you probably want to stay super still for this."

With that, he casts Scorching Ray-- it's far easier to control than other fire-based spells, and he gets three goes at it. Each of the three beams is directed at Syrlya's arm, and away from his body as much as possible, angled so that he wouldn't hit anyone else or... well, anything especially flammable.