This power allows you to sense invisible creatures around you, as long as you have at least as many ranks in this power as they have in their invisibility power. In addition, you gain the ability to sense the aura of death - every time a player kills a monster within 500 feet, plus 5 feet for every monster they've killed the current day, plus 25 feet per rank you have in this power, you will be able to sense their approximate distance and direction. You will also sense the approximate distance (but not direction) of kills made at up to three times that range.
Your sharpened hearing helps you avoid attacks. During cooldown you dodge at 1% feet Defence per rank (added to the 50% from Instinctive Dodge, but doesn't stack with Enhanced Deflection). You also get +5 Defence per rank, doubled to +10 if you're blind, applied before percentages (but without Blind Fighting you still suffer visibility penalties). You lose all of these bonuses while deaf.
This power also gives you access to the 'echo' command, which has the same range as your death/power sense, and will reveal the approximate distance and direction of the nearest creature within range. Every 10 ranks will allow you to sense an additional creature (eg at rank 20 you can sense the nearest 3).