What would happen if a wizard summons a familiar (using find familiar) in the Border Ethereal, and then the wizard returns to the Material Plane (interrupting or ending the magical effects of etherealness)?
Would the familiar disappear due to the distance from the caster, since they are now on different planes?
Or
Does the Ethereal Plane overlap with the Material Plane (Border Ethereal) such that distances are preserved and the familiar remains in the Border Ethereal while the caster is in the Material Plane?
The Ethereal Plane
Its shores, called the Border Ethereal, overlap the Material Plane and the Inner Planes, so that every location on those planes has a corresponding location on the Ethereal Plane. (PHB, p. 301)
Does this make possible the ability of having one's familiar become an ethereal traveler?
Best Answer
The familiar, once summoned, does not have any limitations on where it can go, or what its distance from its owner can be. There's a distance limit for using its senses, and the DM would have to make a ruling on that aspect -- is the ethereal plane within 100 linear feet of the material plane?
But there's no reason you couldn't summon a familiar on the ethereal plane, and leave. Or summon it normally on the material plane, and send it to the ethereal plane by one of several methods. Or summon it in either place, temporarily dismiss it into its pocket dimension, change the plane you're on, and have it reappear wherever you are.