Good day to you, fellow gamers.
Some backstory:
While preparing for a published adventure, I have found that one of the enemies that the PCs will have to encounter have a free ability (as an action of course) to enter Ethereal plane and come back. My PCs are somewhere between 7 – 9 level, and, by design of the adventure, they will have both a time limit on this scene AND the need to destroy enemy in question. By the look of his stats, his best tactic is to jump into Etherealness and wait out for time to pass. The PCs will have to find some way to get him out from\see him on the Ethereal plane in order to succeed in their quest.
As far as my experience of rules go, here is what I know:
- Robe of the eyes, which allows the user to see creatures on the Ethereal plane within 120 feet
- See Invisibility, 2-d level divination, which allows to see into the Ethereal plane
Both of the ways might be unavailable to party during the scene, in which case the loss is guaranteed. I hope to find other ways the creature can be found or forced out of the Ethereal plane.
My party most likely will consist of following race\class combo:
- Dragonborn\Barbarian(Frenzy)
- Halfling\Rogue(assasin)-Monk
- Wood elf\Ranger(Hunter)-Rogue
- Half-Elf\Rogue(Trickster)
- Human\Fighter(BM)-Warlock
- Dwarf\Cleric(Life)
So, basically, the question is this:
What ways, in terms of magic items, abilities, magic, etc, are available for players to interact with Ethereal plane on their level?
P.S. For reasons I can't discuss I have no option to insert MucGuffins for players to succeed, except for information about that enemy and his abilities. So I would appreciate answers regarding to actual rules.
Best Answer
This sounds like a problem with the adventure.
A bit of a frame challenge here, but I feel like this is more a problem with the adventure than the party. 5e doesn't have enough material that you can assume that every party can solve every problem (like you could in 3.5), and assuming that a 9th level party can affect the ethereal plane isn't a reasonable assumption in a normal 5e game.
The problem is that seeing into the Ethereal and affecting the Ethereal are very different things. 5e doesn't even have the old standby of force effects working against Ethereal targets like 3.5 did. It's going to be pretty difficult for a 9th level party to be able to do anything meaningful to an Ethereal target.
Given the restriction of not being able to add Ethereal-affecting items to the existing adventure, here's what I would suggest:
Give the enemy a reason to attack the players.
As you note, the tactically correct option would be to go Ethereal and wait out the party, which would make the party lose no matter what. A way to sidestep this issue is to give the enemy a reason to attack the party despite the fact that it could safely wait out the combat. Is the enemy non-intelligent, like an animal? Does the enemy have a vendetta against the party, and wants to kill them beyond reason? Does the enemy have a goal that involves the death of the party? Is the enemy just dumb, and doesn't think of using his abilities to their greatest effect?
If the enemy has a reason to come out of the Ethereal to attack the players, and uses their Etherealness to improve their combat ability rather than avoid the combat entirely, you're going to end up with a fight that's likely to be more fun.