Undead Knights are enemies that appear in.
They are undead reincarnations of the female knights of Tan Line Island who exploded into the air. They seem to mimic the physiology of revenants who are spirits/skeletal beings that seek out revenge on those who ambushed them. While they do mimic their Pirate's Curse counterparts animations, they seem to attack Shantae with more aggression.
They are the one of the only monsters that wait for the player to come near them so they attack them again. As seen in Hypno Baron's Castle.