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.
This build is used if you wish to support both your attack damage and Ability Power, I suggest lanning mid, Unless there is a kog maw on other team due to his ult giving sight inside your twilight shroud. Maxing out crescent Slash before mark of assassin makes farming much easier. also if your alone having twilight shroud makes it so you can attack minions without being hit by range dps or enemy spells. After you obtain your ult you should look at both sides and check if either one would be easy to gank. If there is gank. you can use twilight shroud to slow and then use your ult to chase and crescent slash just to do some damage. At this point you should probably have a Majai's Soulstealer point. After this you should be able to easily wreck the rest of the game unless you have so feeders on your team.
If you are on bottom lane or top lane no worries. you will level up slightly slower and you are generally squishier. use you twilight shroud to check the grasses when you are entering and you shouldn't die to much. the rest of the game should continue easily getting your first majai's stacked might be harder but when you get some you should be good for the remaining time in the game.
Ps, don't feed ;)
Update: Akali was nerfed so this will most likely not work.