Would this be an ok houserule?

[Werephilosopher]

Transdimensional Power (http://dndtools.eu/feats/complete-psionic--59/transdimensional-power--2956/) lets you hit creatures in coexistent and extradimensional spaces. It explicitly calls out hitting creatures in the Ethereal and Shadow Planes, plus incorporeal creatures and creatures in portable extradimensional spaces, like portable holes. However, it does not limit the meaning of "extradimensional spaces" to just portable ones, so would it be reasonable to allow a creature on the Ethereal use this feat to hit creatures on the Material, since the Material could be said to be "extradimensional" to the Ethereal? And even if the semantics don't work like that, would it be too game-breaking to allow it anyway?

If it matters, the Meditant (http://www.wizards.com/default.asp?x=dnd/psm/20040827c)'s level-9 ability is unlimited time on the Ethereal, but only 3 times per day. I'm wondering if letting the feat work this way would break this, since it means they don't have to expend daily uses to return to the Material Plane and fight.

[jedipotter]

It's fine. I've used it that way forever. And I let it get into Rope Tricks too.

[Psyren]

RAW this will not work, as the "Benefit" section of the feat is where it specifically spells out what you can affect with a transdimensional power.

As for would it be gamebreaking - this largely depends on the power level of your campaign. It's undeniable that a Meditant who can assault his enemies while staying safely ethereal is more powerful than one who cannot. One of the balancing factors of etherealness is that it is nearly impossible for ethereal creatures to affect the material, while there are more ways to accomplish the reverse.

[Flickerdart]

Remember that the meditant can stay Ethereal for as long as he wishes. Letting him attack things from ethrealness would be absurd - such a character would be the perfect assassin, able to get into anywhere and attack with impunity; only a rare few high-level effects would be able to even touch him, never mind stop him.

If you're concerned about meditants needing to use their limited daily ability to return to the Material Plane, let them manifest psionic ethereal jaunt in reverse.

[jiriku]

However, it does not limit the meaning of "extradimensional spaces" to just portable ones

You have misread the feat. Transdimensional power works against any extradimensional space whose opening is within the spell's normal area, whether the space is portable or not. The mention of "portable" was just one example. This means that (as jedipotter noted), it works against rope trick, and also effects like magnificent mansion, etc. Note that the opening to an extradimensional space exists only in one plane, so if someone is inside a rope trick on the material plane and you transdimensional fireball the entrance, you burn them, but if you are ethereal at the time, you do not burn them, because the rope trick's entrance is not located in the ethereal plane.


so would it be reasonable to allow a creature on the Ethereal use this feat to hit creatures on the Material, since the Material could be said to be "extradimensional" to the Ethereal?

The material plane is not an extradimensional space -- it is a dimension. "Extradimensional" is a reserved word in D&D that refers to small spaces that do not exist on any plane.


And even if the semantics don't work like that, would it be too game-breaking to allow it anyway?

I would recommend against it. 90+% of published monsters can be killed without risk of injury from the ethereal plane if you can cast from ethereal to material. This would wreck so many encounters that it's not even funny.

[Dimers]

I would recommend against it. 90+% of published monsters can be killed without risk of injury from the ethereal plane if you can cast from ethereal to material. This would wreck so many encounters that it's not even funny.

More to the point, it would create a deeper divide between power levels within a party and would encourage casters to solo encounters even more. The houserule probably wouldn't hurt a game oriented toward tier 1-2 PCs (and would be an interesting specialization there), but anything lower than that and you get into metagame problems real quick.