Reputation

Not really a skill, per se, an Assassin's deadly reputation can sometimes make attackers rethink their choice of target. Reputation cannot be practiced. It must be earned...

Assassins earn 1% through a successful Insightful Strike.

Assassins lose 1% when they flee, even when caused by a spell (Dread).

Max that can be earned at Hero for Assassins is 75%.

Black Circle Initiates also get a certain (20%??) reputation due to the nature of the Circle but this is not earned and can not be lost.
(Someone needs to confirm the details for BCI reputation and delete this line, as I have not got a BCI to do it myself, and the above is just guess work using help BCI )

What the skill does is when you get aggied by a mob there is a chance (dependent on the % of reputation you have) that the mob will turn and attack one of your group members instead of you, so if you had 100% reputation in theory you would never get aggied.