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.
Reference, might make a guide.
Sheen, ROA, Mercs are core, try to get to Lich and Void. Replace with others to add tankiness or damage. Last Whisper for turret destruction.
Magic pen mastery and utility for more mana regen.
Runes for AP and dodge.
Skills are versatile. Max Grab quickly is you have ranged. Stun for melee. Ulti always.