The Hollow Knight of Frost is one of the many Hollow Knight varieties. As with all Hollow Knights, it only appears at night, and in this case mostly on crystal type islands.
Combat and Tactics
This enemy has two attack patterns. Upon sight, it will walk towards the player. Once it gets close enough, it will launch a bolt of magical ice energy. If the player is close enough, it will swing a sword in an attempt to strike the player. Both attacks can be dodged quite easily. Also, after you dodge its magical ice energy attack a number of times without killing it, it will turn monsters around it into duplicates of itself and the clones are capable of doing the very same thing to other monsters in close proximity.