Saw some questions about lethality and wanted to get out some context on what the changes are and why we're making them.
First, the changes:
Flat armor penetration has been replaced with the new Lethality stat. We changed the name for a few reasons. "Flat armor penetration" as a term has frequently lead to a lot of confusion. It implies that it's good against targets who've bought armor, which is functionally backwards. We've also changed how the stat works a fair bit, so making sure that players understand that something is different has some real value.
Lethality now gives the owner flat pen split between a base amount, and an amount that scales with the target's level.
The current formula is 0.4X + [((0.6X * Y)/18) = Flat Penetration Amount], where X is Lethality and Y is target champion level. This is very much subject to change as we start getting a lot more balance information.
The goal here is to soften the impact of a very ahead assassin stacking a ton of flat pen early, and also reduce the fall-off assassins face over game time, especially when behind.