Syreian the Bonecarver is a level 73 rare vrykul with approximately 15k health. She can be found in eastern Grizzly Hills patrolling a very large area south of Drakil'jin Ruins. I have indicated the area where she patrols in red on the map below. She is also one of four rare spawns int he zone. The others are Arcturis (spirit bear), Seething Hate and Grocklar.
Syreian is part of the Northern Exposure and Frostbitten achievements. She drops Syreian's Leggings which are level 72 bind on equip leather pants with a random enchant. Like other Northrend rares, she also drops Abandoned Adventurer's Satchel, which generally contains about 20 gold, a full stack of frostweave cloth, and often times a few crystallized elements. She also yields a decent amount of experience for leveling characters.
She also really has no special abilities to note, she doesn't hit hard at all. Any one leveling in the area that comes across her shouldn't have any trouble.