You NEEED this (3 e because it's important)
Also an explanation on
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.
Kindred loves Attack Speed.
You are not gonna build that much AD since it would not scale well anyway. That's why you go for Armor Penetration.
Armor is just a little bit of basic resistance (mostly against jungle creeps but also against some attacks).
The magic resistance makes you a little tankier against magic damage dealing assassins who
could oneshot you.
Can be replaced with more Attack Speed if you are sure you won't be taking a lot of magic damage.