Can't seem to find the answer so I thought I would ask.
My PC found a ritual that summons a nightmare. The wording on the ritual is "...the nightmare will serve the person who performed the ritual faithfully for the life of its master."
I know when a summoned creature is killed they return to their home plane and reform over 24 hours.
So, would a nightmare in this case use its Plane Shift racial ability to return to the material plane if the master has not died.
I would say yes, as it specifically says "the life of it's master".