Unlocking Talon's VengeanceBefore you can gain reputation with Talon's Vengeance, you need to complete a pretty long quest chain to unlock the faction. This is done by completing the Falcosaur battle pet quest chain, and once you have the mount and the pet, use these two while interacting with Aviana in Highmountain to unlock the faction.
Because of the length of the quest chain, I'm not going to post it here, but instead link to the Falcosaur quest chain guide. Here you will find all the information you need to unlock the faction.
Getting reputation with Talon's VengeanceTo get reputation, you need to use your Ivory Talon item, which is awarded to you when you unlock the faction. This flags your for a Free-For-All-PvP, in which you can kill any player to receive 1x Mark of Prey. These marks can be traded in to Aviana for 100 reputation per mark.
At Ivory Talon only works on the PvP and Falcosaur areas, but once you hit honored, you can buy an upgraded version which works in battlegrounds as well. This upgraded version has a much lower chance to award marks, but will not turn you hostile towards your own faction.
To get to exalted you need a total of 420 marks, unless you have a rep buff active to increase the gain.