The Fang of the Twins is a two-handed sword (or battleaxe) in NieR RepliCant and NieR Gestalt (NIER), found in the labs under Emil's Mansion. It has the tip of a pike, but two dual axe heads as a blade.
"A giant, accursed axe that was bathed in the blood of young twins before being presented to the gods themselves."
We have been together since birth. When we eat, when we sleep and dream.
We get the same things as well. mommy’s breasts, and daddy’s gentle words.
But we died separately. Me, at daddy’s hands, my sister at my mother’s hands. They cut off our heads, and we died separately.
But it’s okay. Our blood mixed together, and stay in the same axe. We will always be together from now on. Two bodies will return to one.