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.
As you see it isn't possible to build my item build according to the 6 slot build place, so instead it is a priority list of what you should get IF you have space to build the next item with the final item build as:
Blade of the Occult
(in that order)