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.
If you cannot stack up your Mejai's Soulstealer then switch it out for a
You can swap out for or but most of the alternatives are subpar for LeBlanc.
Try to get your team to give you a solo lane, if not a duo lane can work with a stun or slow.
You want to harass as much as possible with your Sigil of Silence and using Distortion or Ethereal Chains to activate the silence.
When you hit 6 you can go for easy kills with your absurd nuke combo of Sigil of Silence > Mimic > Ethereal Chains.
If there are multiple champions attempting to gank you, you can easily escape with Flash and Distortion into a Mimic.
If you are certain that you can burst a champion near a tower down, then just Distortion over the wall into tower range, throw a Sigil of Silence > Mimic into them and make sure to Distortion as fast as you can.