What is Alien Presence to Dragons?

[awesometori]

I am creating an encounter involving young time dragons (http://www.d20pfsrd.com/bestiary/monster-listings/dragons/dragon-outer/outer-dragon-time/time-dragon-young), and I'm looking at the alien presence. And, despite all my googling, I can't find anything that specifically tells me what is alien to the dragon. Is that up to me, as the DM, to decide, based on what is in the dragon's world? Is it any creature that is not a fellow dragon? I'm not finding anything to clarify this, and maybe there's just one little sentence in one little book I'm missing somewhere, that I'm hoping my fellow Pathfinder players and creators can help me out with.

I can't find a generic description of Alien Presence to refer to, or to help me in this scenario. Help with this would be much appreciated. Thanks for reading! :D

[Khedrac]

Since you linked to a Pathfinder site I am guessing that this is for Pathfinder or another D20 variant - in which case you are in the wrong sub-forum. You need the 3.0/3.5/PF D20 sub-forum.
In here you find the AD&D players and some D&D players - but it is a very different D&D (when my answer would probably be "anything from the Dimension of Nightmares").

If I am right you need to PM a Moderator to move this to the other forum (or report your own post).

If I am wrong, you probably need to explain which system you are playing and more about your world.

EDIT: OK, properly reading the Alien Presence entry it seems that a Time Dragon does not belong in the normal world - and it the realization of this that shocks those that encounter them. It would be nice to know what its range is though.

[The Glyphstone]

Looking at the entry, I'm not sure how 'what is alien' matters at all. The actual mechanical effects of Alien Presence are http://www.d20pfsrd.com/bestiary/monster-listings/dragons/dragon-outer and http://www.d20pfsrd.com/bestiary/monster-listings/dragons/dragon-outer/outer-dragon-time and it appears to just be a modified version of Frightful Presence. This isn't an ability of the dragon to sense/affect aliens, the dragon itself is so alien/strange that it affects other people.

EDIT: Outer Dragons page says 30ft x Age Category is the radius.

[Milo v3]

It's the same as frightful presence except that for Time Dragons it creates the following effect "A creature that fails its saving throw against a time dragon's alien presence is staggered for 5d6 rounds (or stunned if it has 4 Hit Dice or fewer)."