What’s the difference between a Master House and a Lordly House? How come the Glovers have vassals if they’re not lords, and why arent they lord when they used to be kings?

Masterly Houses are the Northern version of landed knights. Landed knights have the same military/economic rights to military service, taxes, rents, etc. as lords, but they don’t have some of the broader judicial rights that lords do.

We don’t know why the Glovers were reduced to masterly status – especially since they were once a royal house – but my guess is that it was done to cement Stark authority over their demesne while still operating within the boundaries of feudalism. If it was done early on, it might have been done to emphasize that the Starks were *the* Kings in the North and that petty kings who opposed them would be treated more harshly than those who joined willingly. If done later, maybe it was in response to a rebellion.