Knight

Black Knight
The Black Knight moves erratically around the room and charges toward Isaac when in line of sight, and can only be damaged from behind. Tears that hit its front are reflected and can damage Isaac. Upon colliding with an obstacle after charging, the Black Knight will knock itself back and send out 4 streaks of purple fires in the cardinal directions. At this point the Black Knight will be stunned for a few seconds, making it a good time to strike.

Loose Knight
The Loose Knight moves erratically around the room and can only be damaged from behind. It splits into an Empty Knight and a Pon upon death.

Empty Knight
The Empty Knight moves erratically around the room and charges toward Isaac when in line of sight. It cannot be damaged, but will die if the corresponding Pon is killed.

Pon
The Pon hops around the room, leaving pools of damaging red creep.

Trivia

 * The Black Knight's facial armour resembles The Visage.