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.
Get torment first. More damage early.
Start with two Kage's for the quick 50 AP and the extra gold will be needed.
Mejai's next because you kill. That's what you do.
Either you get the cooldown reduction boots, Magic pen. boots, swifties, or mobies... Your choice.
Lich Bane and Deathfire Grasp are a must... For killing champs with over 3k health.
Get the new Deathcap next... It's just HaX...
The crystal scepter just for giggles. :P
Use Torment and auto to harass your opponent. Gold farm while they're gone.
In team fights, drop Nevermove, then torment who is going to be focused and Decrepify them. If they're not dead yet, auto with Lich Bane and it's over. Use ult when health gets below half, then clarity for the lost mana, and push.