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.
Start with a sapphire crystal and a health potion and a mana potion. Max out your dark matter first. Then use your baeful strike to farm ability power from last hitting minions. First Stun your target with Event horizon. Then use your dark matter while the target is still stunned. Use your baeful while the dark matter is hitting the ground. Only use your ulti if the target has AP otherwise you should save it. For tight situations, try to lure your opponents to an edge or a wall, then flash to the other side.