Pei-Ziao the Pernicious is one the leaders of the Marauders and one of the Bosses of Atys. He is one of the 6 Marauder leaders that players can kill to obtain the Marauder armour, and one of the 4 that give Marauder heavy armour (the other 2 give light armour). His heavy armour is purple.
His lair is Highland Impasse in Knot of Dementia, and he cannot be drawn out of his lair. His special powers are:
He can use his dagger as a ranged weapon.
He cannot be harmed by anyone who is not inside his lair.
His special attack stuns everyone who is inside his lair for a long time.
And like all Marauder leaders, he has huge health and huge health regeneration, so that it takes lots of elementalists to kill him.
The usual strategy to kill him is to position all elementalists inside his lair along with a single meleer to distract him, and all healers outside his lair. Then it is just a matter of having enough fire-power and healing to beat his regeneration.