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.
sivir has died and come back as a vampire. with life steal and attack speed mixed with ricochet you would restore a massive amount of life for each hit per enemy. also with on the hunt you would gain the boost making your life not drop a bit. good for solo lanes and quick champion takedown (2 or 3).