Information:
These guys are fast, hit you faster, and just plain mean. They usually come in groups of 2's and/or 3's and will kill most meleers that aren't careful. They have also learned how to cure themselves of poison.

How to kill:
Bards: Provoke them onto other Terathan's, then use magic or a bow. This is the most efficient way of killing them. Just beware of other Warriors/Avengers spawning in and have your Peacemaking macro ready.
Archers: Poison, then use your bow to kill them. If they cure, re-poison and continue using your bow.
Mages: Flamestrike/Energy bolt/Energy bolt; dead. Enough said.
Warriors: Be ready to heal and bandage. Cast Poison on them, then beat on them with a decent Broadsword as quickly as possible.Tip: Firefields do wonders if you can ever get them trapped.

Loot:
180+ gold, chance of magic item, chance of treasure map, chance at a moonstone. They don't spawn magic items like they used to. Not worth your trouble if you are looking for loot. Don't be surprised if the price of magic weapons go up now.