Borys owns a triple-headed flail called Fleshrender. It was once owned by Aoric Fleshrender, Bane of Galefridus, Flail of Gavriel, Harbinger of Agony. He was a veteran of the black baron. The shaft and chains are black iron, the heads are lustrous horned skulls, and crimson runes run down the haft. The Order of Solis gave it to Borys as a reward for joining the order and helping during the quest dealing with the Beast of Barural's Delve.

The Flail is a superior melee weapon with a +3 proficiency bonus, doing 1d10 dmg, versatile, weighing 6 lbs. It is a +1 magical weapon giving +1 to attack and damage rolls, and an additional 1d6 damage on a critical hit.
The Flail is a (something) weapon, with an (encounter or daily?) power where, as a free action, when an attack hits a bloodied ally within 10 squares of the wielder, they can gain a +2 bonus to attack rolls and +1d10 to damage rolls against the attacker until the end of their next turn.

(Not sure which book this item comes from)