Fae'shiel is ready for level 5.
I should note that while the Bladebound Magus entry says that a DM is supposed to pick the additional languages that the Blackblade learns, I thought it would be fitting that the Blackblade learn Dwarven as it is apparent that Fae'shiel's blackblade happens to be a dwarven craft sword (as per developments in my current and last adventure). But if the person reviewing my characters level up disagrees with that assessment, feel free to have it learn a different language instead.