The Warhammer of Zillyhoo is a Hammerkind weapon, and as such, will either slot into your Hammerkind Strife Specibus or create a new one. Attempting to equip the Warhammer of Zillyhoo when your Strife Specibus has four other specibi will result in the weapon being captchalogued.
How to obtain:
Hammer && Problem Sleuth Poseter=> Warhammer of Zillyhoo
Sledge Hammer && Problem Sleuth Poseter => Warhammer of Zillyhoo
Bugs
There was a bug with the hammer that allowed it to be made with && even though it is supposed to be || alchemy.