Tome of the Stilled Tongue

This thick leather-bound volume has a desiccated tongue pinned to the front cover. The first few pages are filled with indecipherable scrawls. The remaining pages are blank and pristine.
Once attuned, you can use this as a spellbook and an arcane focus. In addition, you can use a bonus action to cast a spell you have written in this tome, without expending a spell slot or using any verbal or somatic components. Once used, this property can't be used again until the next dawn.