The Nailhammer is a Hammerkind weapon, and as such, will either slot into your Hammerkind Strife Specibus or create a new one. Attempting to equip the Nailhammer when your Strife Specibus has four other specibi will result in the weapon being captchalogued. The Nailhammer deal 3 base damage.
How to obtain
Nails && Hammer => Nailhammer