Iudex Gundyr

Iudex Gundyr is a boss in Dark Souls III.

Location
Found in the Cemetery of Ash, near the entrance to Firelink Shrine. He is first found kneeling down and is immune to damage. Once the sword in his chest has been removed, he will rise and the battle will begin.

Lore
Once a champion, Gundyr became a judge, awaiting the arrival of chosen ash to give onto them a coiled sword. He received a special halberd upon being charged with his duty and was restrained with a steel chain. As Iudex, Gundyr judged any Unkindled seeking to enter Firelink Shrine. Sometime during his vigil, he became host to a writhing corruption that possessed a will of its own.

Strategy
Gundyr cannot be damaged until the Coiled Sword has been removed from his chest. Once done, he will begin to rise and is vulnerable to damage, even though his health bar won't appear until he has taken up his weapon. Lay into him during this, as he can't retaliate in any way; by the time his health bar appears, you may have already dealt substantial damage to him.

Trivia

 * Iudex is Latin for 'judge', an apt name for this boss as it seems to decide who is worthy to access Firelink Shrine.