Viletta Vadim wrote:
Detect Magic, Detect [Alignment], and so on can detect various auras that the target may have, though it takes a while to pinpoint, and by then, there may already be a knife sticking out of your throat, which is bad.
If the stealthy type is supplementing mundane stealth with illusions, then True Seeing pierces those defenses.
Mindsight, also from Lords of Madness (page 126), is not on the list of things Darkstalker protects against. It requires telepathy and automatically detects every intelligent creature within range of that telepathy. Easy ways to acquire telepathy include a Psion telepath alternate class feature at level 5 and the Mindbender PrC from Complete Arcane (never take more than one level in that class). Unfortunately, Mindblank blocks Mindsight.
The psionic power Touchsight is also not on the list of stuff Darkstalker protects against. The only real way to hide from Touchsight is through incorporeality, which is probably going to be really glowy on Detect Magic or else require the character in question to be a ghost, subject to Detect Undead.
A Psion telepath with the Telepathy ACF as a passive scan and Touchsight as an active scan, possibly paired with a source for Detect Magic and Detect Undead will pretty much be able to detect anything.
Ravenot wrote:
Scent ability, and if I remember Blindsense has a way of seeing past stealth too.
Darkstalker allows stealth checks against Scent, Blindsight, Blindsense, and Tremorsense. It's a feat that was too long in coming, since there have long been way too many, "You fail, no matter how good you are," effects against stealth.
Thanks Viletta, and everyone else too for the excellent ideas! I could also assign "immunity to sneak attacks and critical hits" as a creature's ability (to an existing creature), essentially advancing it, and then adding a CR or 2. But that's cheap.