Reduvius Dagger (Elden Ring)

Is it possible to equip a dual weapon in the game (one weapon in each hand)?

In the game, I stumbled upon a red phantom, from which the dagger of Reduvius fell out. The phantom had them both in the left and in the right hand.
I can assume that the phantom is (most likely) scripted, and more like a boss... but still, maybe I don't know, but there is a way.

Thanks in advance for your replies!