This staff cannot be used as part of a Hero's attack action on their turn, and can't be used for dual wielding. Holding it grants the wielder the following powers:

Counterattack - 1 reaction, when hit by an undefended melee attack within Reach: 1: Attack the enemy that hit you for 2d8+STR.

Right back at you (1/encounter) - 2 reactions, when hit by an undefended melee attack: Attack the enemy that just hit you with the exact same attack they hit you with.