You mean WizWrm.
I like the idea, but it seems that either I'd be expecting to be fighting outsiders or be caught totally by surprise, as they aren't particularly common. The ability would only confirm that I'd gotten within bow range of what I was looking for. If I wasn't specifically hunting one, it probably wouldn't occur to me to check for auras, as a paladin with
detect evil might think to check each new area they enter, just on general principle, especially with unlimited usage.
How about:
Sense Demonic Taint - Long exposure to the peculiar magic of outsiders has left you sensitive to their unearthly presence. You can always sense the existence of outsiders within 60', but will know no details; only the number of auras in very general terms. Three times per day, as a full-round action, you may attempt a Spellcraft check (Will save? Charisma check?) with a DC equal to 10 + HD of each outsider to determine the strength, direction, and specific number of auras. In addition, you may do this to sense lingering auras, as defined in
detect magic, with the caster level equal to the hit dice of the outsider for the purpose of determining aura strength. This ability will not detect outsiders native to your plane.
Example:
Kaelthrong the Nar Demonbinder is walking through the Underdark, when suddenly he sniffs something foul on the subterranean wind. He focuses his mind and reaches out, rolling a 23 for his Spellcraft check. This is enough to tell him that a moderate aura is northeast of his position; indeed, it is a glabrezu, a 10-HD demon. However, it is not enough to tell him that it is accompanied by a marilith, which is a 14-HD creature, requiring a DC of 24 to sense.
It's no worse than the Sensitive feat from AU, at least, and definitely less than a paladin's
detect evil radar.
