Truth be told, the moment she saw the Bowmaster producing a Shadowmesh Arrow from his pack, Xin Yu had been a little bit worried. Fateless had told her a little about Spell Arrows.
There were lots of Spell Arrows available at the Alchemists' Guild which increased a Bowmaster's attack damage, or gave them the ability to deal elemental damage; and then there were items like the Shadowmesh Arrow, which produced incredibly powerful magical effects.
The Shadowmesh Arrow was effective even against Boss monsters, but it was prohibitively expensive! Ten thousand gold apiece for a one-use consumable item—the average player couldn't even consider it.
The Shadowmesh Arrow had another invaluable quality: when Binding a target, even if they had defensive magic such as a Barrier active, they would still be subject to the effect!