Tai recognizes it as a gem that is among the type used by necromantic growing rituals. He does not, however, figure much more out other than it's *not* a regular item. He knows it is arcane in nature.
As Omar concludes his search, Xylona produces several scraps of paper and lays them down for the others to see.
Spoiler: Scraps of Map
I found this in the burnt remains of the tent. What do you make of it?