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.
You will know you were successful because you will receive a message that says in cyan: Your Reputation Grows...
There is also a quest in Midgaard that involves completing Assassin Contracts, and rewards with 1 reputation point.
Assassins lose 1% when they flee, even when caused by a spell (Dread).
Max that can be earned at Hero for Assassins is at least 80%. Updated: Max reputation for Lord Assassins is also 80%.
You can check your reputation by typing 'slearn reputation'.
Black Circle Initiates also get a certain reputation (20%) due to the nature of the Circle but this is not earned and can not be lost.
What the skill does:
Your reputation percentage represents the chance that an aggressive mob will attack (aggie) a groupie instead of you; if you have 100% reputation, in theory, you will never get aggied in a room with living groupies.