Blindsight

[Lellindil]

blindsight (ex): using nonvisual senses such as sensitivity to vibrations, scent, acute hearing, or echolocation, the creature manuvers and fights as well as a sighted creature. invisibility and darkness are irrelevant, though the creature still can't discern etheral beings. the ability's range is specified in the creatures descriptive text. The creature usually does not need to make spot or listen checks to notice creatures within range of its blindsight ability.

it basically comes down to what kind of blindsight the creature has. if its a dragon there is nothing that can fool it besides being etheral because it combines all forms of blindsight.

a dragon can ascertain creatures by nonvisual means (mostly hearing and scent, but also by noticing vibration and other environmental clues) with a range of 30ft X the dragon's age category.

it should say under each monster what kind of blindsight it has. but the only ways to fool them are:

sensitivity to vibrations: flying or levitating
scent: i beleive that there is an item in MotW that fools scent
accute hearing: silence (maaaaybe this could be fooled by an insanely good move silently roll but that would have to be the DM's decision)
echolocation: silence again

both of the above quotes are from the MM

 

[Janos Antero]

sensitivity to vibrations: flying or levitating
scent: i beleive that there is an item in MotW that fools scent
accute hearing: silence (maaaaybe this could be fooled by an insanely good move silently roll but that would have to be the DM's decision)
echolocation: silence again

Actually I think sensitivity to vibrations in the sense meant by Blindsight is air vibrations or movements, otherwise it's really tremorsense. Granted I assume it's poorly worded, but I can't see why they'd have both abilities unless Blindsight didn't cover the same turf.

Sensitivity to currents and changes in air movements felt through the skin, or heard maybe?

 

[Lellindil]

thats a good point. yea i think ur right

 

[Saeviomagy]

Personally, I'd say that, at present, every creature with blindsight cannot automatically see hidden creatures, and that they use either their listen or spot skills to pick them up, whichever is better.

Also, I'd consider introducing the rule from d20 modern which stats 'you may only hide if you have more than X concealment or Y cover from your opponent". It's assumed in 3rd ed, but it's not codified.

This means that a rogue who hides in some shadows wil fail to hide from a creature with blindsight, but one who hides behind a rock will succeed. (the blindsight would negate the concealment of the shadow, and therefore render the thief unable to hide)

Allowing blindsight to completely trump the hide skill is about as dumb as letting invisibility completely trump the spot skill. It's not done, it just adds significant modifiers to the rolls involved.