The Abandoned

Ruins of Lordaeron
Beyond King's Alley, choose the side encounters before finishing with Rath'mael. Approach the market statue from Lordamere Overlook for The Abandoned's wave event. Viktor the Vile is optional: the chimney in the house southwest of the overlook starts the waves that bring the boss out, so recover health and mana before touching it. Clear nearby groups before engaging Bjork's central patrol rather than combining the fights.
The Abandoned
The Abandoned follows the market statue's waves and tests whether the group can stop Life Drain while Frost Nova roots nearby players.
Abilities

Frost Nova
Inflicts Frost damage to nearby enemies, immobilizing them for up to 8 seconds.
Frost Nova roots nearby enemies. Healers and ranged damage should keep back from The Abandoned rather than joining the tank in its reach.

Life Drain
Use a stun as Life Drain begins. Health taken from its target returns to The Abandoned, so letting it continue also prolongs the fight.
Tank- Pick up The Abandoned when the statue waves end. If you have a stun, hold it for the start of Life Drain instead of spending it as the boss arrives.
Healer- Stand back from The Abandoned so Frost Nova does not root you beside the tank. Keep the Life Drain target alive while the group stops the cast.
Damage- Reserve a stun for Life Drain. Ranged players should stay back from Frost Nova rather than moving beside the tank to attack.