Esh the Mind Lasher is a named undead dragon that can be found in the middle of the Northern Deadlands. He is part of the Rite of Passage, and can usually be found alone, unless a Wraith Master wanders near his path.
A fight with Esh the Mind Lasher is pretty straight-forward fight. Occasional kiting may be useful for healing, but otherwise staying close and hitting Esh is the best way. He doesn't possess any sort of heavy-hitting attack to worry about like Gold Rage. He is more of a caster, so getting in close for melee is generally the best tactic. In case of the occasional Wraith Master interruption, just take out the Wraith Master first, as it is actually more dangerous than Esh (and certainly easier to kill).