Lichbane will alow you to fast push turrets after you get a kill. Use this build if you want to take down towers after you pick off people. This build is also good if you miss a skill shot, you can proc the lich bane with a basic attack, which will proc liandry's, doing a good bit of damage. The weakness in this build is the lack of sustain, no mana or spell vamp. You can always supplement with a chalice and revolver if you feel you need it. If you don't get chalice, make sure your jungle knows you need blue.