Faolan nods slightly. It isn't a lot more than they knew before, but it's more than they'd have had if Sirius hadn't tried.

"For the preservation maybe?" he wonders aloud. "Unless the specific herbs maybe have some sort of meaning..." He doubts it though. He doubts that whoever was sending the message would have done so in the choice of herbs they'd have included. The severed head was message enough in and of itself, after all. The question was, who? And of what?