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 will allow you great mana regen and damage early in the game that should propel you through into the latter stages of the fight with an edge against just about all play types due to the large amount of magic penetration and ability power. Also this build will allow you to stand in and bully your opponents with abilities due to the 5 mana/ second you get off of the archangel's staff. You will want to farm gold as often as possible making it easier to gain all the items in the build.. you will notice that after the purchase of zhonya's ring in this build that you will have above 350 AP if not closer to 400 if you are doing well with your Majai Soulstealer. I usually have around 5 stacks at this point but i'm sure that many of you can do better. Finally the Voidstaff gives you that extra magic penetration stacking with the boots. This will negate most of the items tank's use and make you very useful to your team in starting or even finishing enemies off (important when trying to max out your Soulstealer). I listed the last item on this list as the guardian angel.. I do not always use this item. I like to jump between this, the rod of ages, and the haunting guise (due to it's low cost and extra magic penetration) so feel free to do your own modification with this last item and polish it however you choose.