Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This build is mainly for when you either start to steam roll or know for a fact you are going to steam roll. Picking up rage blade gives you some decent tower dmg for when everyone is down from your steam rolling. Leviathan is there for survivability because you will make up for the loss of AP when you reach 20 stacks on Majei's. Lich bane is obvious...
Skill order for ganks
Mark of assasin
Throw Shroud in direction they are running
Rinse repeat untill the whole team is dead
Putting on mark of the assassin before dashing compromises distance for much better burst dmg output.
Try it out and rate. Lane with someone that has a slow or a stun. First blood is an easy task when you rune her out to have both passives active at level one.