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.
The last item, abyssal scepter, is a totally situational item it is mainly for teams with more AP if you are facing a more ad team you might want to take a Zhonya's Hourglass over the abyssal scepter because depending on the team you will most likely get enough enough magic resist from Aegis and Guardians angel to cover the 1 or 2 enemies that are magic damage and visa versa for an AP heavy team. However the rest of items are most likely going to be core items because the defensive items give good mixes without changing at all.