Invisible opponents.

[Bagpuss]

What happens when someone tries to move into the square of an invisible opponent?

What happens when a Fighter or Paladin correctly target the right square, can they mark the invisible opponent?

Do invisible opponents provide cover for their allies?

Does an invisible ally count for abilities that depend on having adjacent allies, even though you could be completely unaware they are there?

[Kordeth]

Originally Posted by Bagpuss

What happens when someone tries to move into the square of an invisible opponent?

They can't move into that square and they know an invisible creature is there. If the invisibility is merely being hidden thanks to a Stealth check, the creature is no longer hidden from that character.

What happens when a Fighter or Paladin correctly target the right square, can they mark the invisible opponent?

Yes.

Do invisible opponents provide cover for their allies?

Yes.

Does an invisible ally count for abilities that depend on having adjacent allies, even though you could be completely unaware they are there?

Unless the power explicitly says "adjacent alkly you can see," yes.

[sukael]

Keep in mind that as per the errata, you know the square an invisible creature is in unless they actively make Stealth checks. (Which they can do at any time due to having continuous total concealment, but...)

[Bagpuss]

What errata I've check the Updates for "invisible" and couldn't find anything.

Ah they have updated the update again..

[sukael]

Originally Posted by Bagpuss

What errata I've check the Updates for "invisible" and couldn't find anything.

Ah they have updated the update again..

http://www.wizards.com/dnd/files/UpdatePH.pdf

Page 10.

[infocynic]

Originally Posted by Kordeth

They can't move into that square and they know an invisible creature is there. If the invisibility is merely being hidden thanks to a Stealth check, the creature is no longer hidden from that character.

How could this actually arise without teleportation? If the creature is stealthed and in an adjacent square that you can move to with a single move (if it's not adjacent, you aren't trying to enter its square yet), then you would (it seems to me) have unbroken line of site to it (aka it has no cover or concealment from you), which would break stealth at that point, before you even try to move into it.

[Saeviomagy]

Originally Posted by infocynic

How could this actually arise without teleportation? If the creature is stealthed and in an adjacent square that you can move to with a single move (if it's not adjacent, you aren't trying to enter its square yet), then you would (it seems to me) have unbroken line of site to it (aka it has no cover or concealment from you), which would break stealth at that point, before you even try to move into it.

A quick read of some of the rogue utility powers will show you a bunch of ways that this might occur.