Watcher Knight

Behavior
The Watcher Knights have three attacks:
 * Double Slash: Watcher Knight will swing their giant nail twice. Watcher Knight will swing horizontally first and follow it up with an overhead slash. Watcher Knight does move forward slightly with each swing.
 * Roll: A Watcher Knight curls up into a spiky ball of death and rolls along the floor of the arena until it hits the opposite wall. They are immune to Nail attacks while rolling, but can still be damaged using Spells.
 * Bouncing Roll: Watcher Knight curls up into a spiky ball of death and bounces twice. When they do this attack, Watcher Knight will attempt to target The Knight, which can mean that Watcher Knight may simply bounce in place rather than travel around the arena. The first bounce takes Watcher Knight to the top of the arena and the second bounce takes them only to the middle. Similar to the Roll attack, they are immune to Nail attacks while bouncing, but can be damaged using Spells.

Trivia
Рыцарь-бдитель
 * Given their name, they are presumably the deceased elite bodyguards of Lurien the Watcher.
 * Combined, the Watcher Knights have the highest total health of any other Boss in the game except for Dream Bosses, The Radiance, and Nightmare King Grimm.
 * The Watcher Knights are one of the few bosses who have to be defeated in order to beat the game.
 * They are referred to as "Black Knight" in the game files.