MarauderX said:
Forgot to add that the game isn't set in Eberron.
A private extradimensional space was brought up in the context of defending against middle-of-the-night attacks on high-level PCs, correct? In that case, even though we aren't in Eberron, it still is an option. Avaya does have Rope Trick, after all. We've barely used it, but it is an option for relatively safe resting.
(We don't have any Bags of Holding or Portable Holes, though we do have a Quiver of Ehlonna that we could do without. Still, there is no rule that such objects cause any problems when taken into an extradimensional space -- just that two specific objects interact with each other.)
Other thoughts:
1) You've banned Teleport, so we're relatively safe from scry-and-fry
2) Even if Teleport worked, Grimnyr does have Detect Scrying active every day, which is automatically successful at detecting scrying
3) If Teleport worked, we'd never spend a night away from our strongholds and we'd have the strongholds warded by Mordenkainen's Private Sanctum, Forbiddance, Hallow tied to Death Ward, and Dimensional Lock.
It's not impossible to surprise us, but it's not trivial.
These defenses are all core and all within our means. There are plenty of defenses that high-level characters can use to ensure that they are not attacked by surprise while sleeping -- which is how it should be, as we certainly aren't ever going to catch a certain great red wyrm by surprise while she's sleeping.
Buff-Scry-Teleport is actually one part of the arms race that defense wins. There is no "Superior Teleport" that lets you break through a Forbiddance or Dimensional Lock. There is no "Superior Scrying" that is as good as Scrying but that Detect Scrying can't pick up and Private Sanctum can't block.