This enemy, found only in the two hallways adjacent to the clock room, are extremely dangerous. Their attacks consist of: An overhanded slash, a rapid-fire thrusting attack, or a wave of blue flames.
If they fall under damage, they will raise a shield and be completely immune to damage for the duration, which is only a matter of seconds. However, if they continue to take damage, they will keep raising their shield. While this is tedious, it provides a way for Alucard to defeat them without fear of counterattack.