Deathbringer

The boss of Warlord Level, Pit #9.
Next #10.

Deathbringer attacks in melee range. Deathbringer never retreats.

To all vocations: stay diagonal and watch out when doing attacks like Exori or Ethereal Spear as you may get exhausted and unable to heal so make sure your hit points is full before using those attacks.
Druid and Sorcerer: Use Magic Shield and try to shoot Heavy Magic Missile runes or Energy Strikes since it's weak against that element, Energy Beam deals great damage but it's dangerous as you stand on the way and vulnerable to waves. Bringing some Stone Skin Amulets might be handy. Using an Energy Wall and run over it to make Deathbringer run around is a good strategy (also works for paladins). But be careful: Deathbringer takes a lot of time to kill for mages and don't let your mana low.
Knight: Melee and use Whirlwind Throw (makes you waste more potions) or Fierce Berserk.
Paladin: Shoot Assassin Stars and Divine Missile.