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.
survivability and items
you see i put archangel early for most mana bonus as soon as possible so as soon as possible max ap available out it. and not to get oom very quickly, also a soul shroud early in build so i can't die quickly. thne i get a will of the ancients, so my bomb, that will eventually blast a whole minion wave at once, heals me as well, and you'd be a better support with it because your lane mate will also advantage the 25% spell vamp of it. and at last you get zhonya's hourglass that if it happens you get main targeted you disable the target and you keep alive as a support.