Spell range unlimited

[Adjoint]

Do spells with range unlimited require line of effect? Can they be used to target a creature on another plane?

Specifically I'm wondering about the spell nightmare, which doesn't seem to have any clarification in its description.

[Kayerloth]

Short answer no.

But this might help at least for part of your questions:

CRB,Magic,Spell Descriptions,Range wrote:

Unlimited: The spell reaches anywhere on the same plane of existence.

Some spells it seems to make little sense to talk about LOE at least in the normal sense. Very little should be able to physically get in the way of a spell like Nightmare. It's hard to see how even being in a closed off room with 5ft thick granite walls would have any effect of Nightmare reaching its target.

Doesn't make sense for a lot of Divinations as well unless the closed off room was also bunkered in behind lead layers or other measures that interfere with divinations as noted in the section on divination magic. Again why would it make sense for something like Discern Location to get blocked simply because your target is in a deep underground bunker but without any magical protection in place. Those spells all do have another thing in common though ... fairly strict requirements about properly identifying the target.

[blahpers]

Pathfinder does a poor job of identifying which spells require line of effect and which do not. It's something we've always had to take on a case by case basis.

[Kayerloth]

Indeed it's fairly obvious in some cases like Fireball. But a lot of them it's less than obvious to 'this doesn't make any sense applied here' category.

And in case I wasn't clear up thread the "Short answer no." was with respect to the specific case of Nightmare.