[quote=Asuras]
It summons these specific types of human-like phantoms that are always one of two variations:A) A heavy armor dude with an ultra-greatswordB) Med-armor dude with a large shield and halberdThese enemies also appear in Aldia's Keep in a similar manner as they do during the Mirror Knight boss; through mirrors. They're relatively weak in terms of defense and health, but can throw out some considerable damage.I managed to beat Mirror Knight on my third try, but I must say he is one of the most difficult bosses in the game, even with NPC aid.
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While this is true, the boss can, and will, summon players within your Sl range(and in NG, your SM range) if they place their red summon sign down in the hall before it. I had it summon a few players in my fight with it.