An arrow. Elven of course, because who else would be this fancy with a throwaway? I've talked weapon talk with traders before, and the squiggly scratching means "make you dead," or near enough. Well made. Have to be, to keep its shape since whatever ancient sod-around its from. All I know is, there are centuries of nocks in the walls I have to patch. They keep an edge if they don't hit stone. Tell the men to mind their fingers. They got fresh blood on this one.
Arrow stuck to the slates on the awning of the veranda surrounding Skyhold's garden, near the north-east corner, somewhat close to the tiny chapel. It can be reached by first going up the rampart walkway nearby and then jumping down on the awning, or going through the doorway that's initially blocked by scaffolding, located on the left hand side of the balcony where Vivienne usually stays. The second method is a little further and requires the scaffolding removed for the doorway to be accessible.