At 3rd level, the bladebound magus' gains a powerful sentient weapon called a black blade, whose weapon type is chosen by the magus. A magus with this class feature cannot take the familiar magus arcana, and cannot have a familiar of any kind, even from another class.
Instead of the normal arcane pool amount, the bladebound magus's arcane pool has a number of points equal to 1/3 his level (minimum 1) plus his Intelligence bonus. This ability changes the Arcane Pool class feature and replaces the magus arcana gained at 3rd level.