What would happen if a wizard calls a familiar in the Ethereal Plane and then returns to the Material Plane?

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?

How do Ethereal objects/creatures work on the Outer planes?

The Ethereal doesn’t border the Outer Planes, and thus spells that allow you to access the Ethereal fail. However some creatures or objects have Ethereal parts to them. What happens to them?

For examples of how this situation can arise:

  • in one adventure set in the Outlands, there is a living trap of scorpions disguised as gold coins. The stingers are described as “Ethereal” even though it takes place on the Outlands. (Or was this detail a mistake?)

  • an Ethereal weapon or creature is forced through a portal

Can a ghost possess someone in the material plane while in the ethereal plane?

The possession ability of a ghost (DnD 5e) states that it can possess one humaniod it can see within 5ft.

I interpreted that a ghost could use its possession ability from the etherial plane itself, since the ghost is visible on the material when in the etherial plane and as such can see the creature. Like this it is possible for the ghost to come up to a humanoid without being able to be hit and possess the creature unhindered.

If the ghost gets shunted out I rule that it ends up in the material plane as the ghost has to enter the body of the creature (who is in the material) while possessing.

However, one of my players mentioned that it is an action for a ghost to change from the material to the etherial and vice versa. He then argued that the ghost should enter the material plane first as an action first before having to spend another action on the next turn to attempt to possess a humanoid.

I can’t really find anything specific that tells that one or the other is true. Obviously the former method is more powerful and while I don’t want to be unfair to my players, I think it is also a whole lot more interesting.

Can a Divination wizard in the Border Ethereal use the Portent feature to influence rolls of creatures on the Material Plane?

A particular School of Divination wizard is native to the Ethereal Plane (he was created by a wish spell replicating simulacrum cast on that plane).

While this wizard is in the Border Ethereal, can he use his Portent feature to affect the rolls of creatures on the Material Plane?

Is there any mundane way to travel from the Border Ethereal of a plane to the plane itself?

Say a commoner with no spells, class features, or magic items is Plane Shifted from the Material Plane to the Border Ethereal.

The DMG makes mention of "curtains" that allow travel from the Deep Etheral to the Border Ethereal, but nothing of any portals in the Ethereal plane itself.

Is there any way for this individual to return to the Material Plane?

Can I shadowstep to the Ethereal Plane if I can see into it?

I am currently playing a Way of Shadows Monk in D&D 5e and now have the Robe of Eyes. I am loving the MadMage campaign.

Since the Robe of Eyes says

You can see Invisible creatures and Objects, as well as see into the Ethereal Plane, out to a range of 120 feet.

And Shadowstep says

When you are in dim light or darkness, as a bonus action you can teleport up to 60 feet to an unoccupied space you can see that is also in dim light or darkness.

Does this mean that I can use Shadowstep to enter the Ethereal plane, scout around and then Shadowstep back in on the following round?

Can channel divinity affect a fiend in the ethereal plane?

In a fight with a Night Hag coven one hag uses the Heartstone to become ethereal, I know that divine sense can’t reach into the ethereal plane and sense her. But can a Channel Divinity affect her?

For example, the Oath of the Ancients paladin has this Channel Divinity option:

Turn the Faithless. You can use your Channel Divinity to utter ancient words that are painful for fey and fiends to hear. As an action, you present your holy symbol, and each fey or fiend within 30 feet of you that can hear you must make a Wisdom saving throw. On a failed save, the creature is turned for 1 minute or until it takes damage.

A turned creature must spend its turns trying to move as far away from you as it can, and it can’t willingly move to a space within 30 feet of you. It also can’t take reactions. For its action, it can use only the Dash action or try to escape from an effect that prevents it from moving. If there’s nowhere to move, the creature can use the Dodge action.

If the creature’s true form is concealed by an illusion, shapeshifting, or other effect, that form is revealed while it is turned.

Will it make the hag turned?

How many creatures can go to the Ethereal Plane via Etherealness cast at 8th level?

The spell etherealness allows you (the caster) to travel to the Ethereal Plane for the duration of the spell (8 hours). It has a range of Self, so you cannot target someone else if cast at its base level (7th level).

However, if you upcast it with an 8th level spell slot, it says (PHB, p. 238):

At Higher Levels. When you cast this spell using a spell slot of 8th level or higher, you can target up to three willing creatures (including you) for each slot level above 7th. The creatures must be within 10 feet of you when you cast the spell.

Where it says “including you”, does this mean that:

  1. you can only target two other creatures, because one of these three creatures must be you, or
  2. you can target three other creatures, but you’re going with them (i.e. you can’t just dump these three creatures on the Ethereal Plane whilst you remain on the plane you were all on moment ago)?

Since I’m a cleric in a party of 4, I want to know if I can bring the entire party (me plus my 3 allies) into the Ethereal Plane or whether one of my allies has to be left behind…