One of the biggest changes in this most recent test realm patch was a change to the way both magic and armor penetration affect damage. This is possibly the biggest change to the game that I’ve seen, so I’ll try to cover it in as much detail as possible over the course of the next few days.

First, you need to understand the current system. The current system is based off a couple stats. There’s flat penetration and percentage-based penetration. Flat penetration reduces defensive stats by the same amount regardless of how much defense your target has. Your runes are flat penetration, in the case of armor giving up to 29 armor penetration at level one. That’s a big deal considering most toons have 25 or less armor at that point in the game. That’s also the reason for the change. Riot didn’t like that you could potentially deal “pure” damage to another level one player, so they changed it. The old system also worked based on your armor number. If you got an item like Last Whisper, it would reduce your target’s armor number by 40 percent. If he had 25 armor, he would now effectively have 15. If he had 100 armor, it was down to 60. That’s important because the amount of damage reduction given by armor does not scale linearly. At 100 armor you take 50 percent of the damage dealt. It takes 300 armor, though, to bring that number down to 25 percent. In the new system, penetration affects defense differently.

The new system allows for percentage-based penetration only (current runes will be changed to a percentage to adhere to the new system). This system also affects damage reduction based on the percentage of damage reduced, rather than the defensive stat number. This means penetration scales more quickly the more defense your target has. Here are the new stats according to Phreak:

Against 100 armor, the old Last Whisper had you deal 62.5% damage (from 50% without). The new one has you deal 63%. Void Staff is slightly higher.

Against 200 armor, old Last Whisper dealt 45.45% damage (from 33%). New one deals 50.67%.

Numbers aside, the point is that you will not hit squishies as hard in the early game because you will not be able to reduce their armor significantly but you will hit tanks harder the more defensively they build. Does this seem problematic to you? It should. The whole balance of the game rests on the fact that the greatest threat – carries/casters – are also the easiest to kill. Tanks exist to provide a point of initiation and control for a fight so that those squishy damage dealers can stand back and deal damage from safety. This change dramatically shifts that balance.

Now granted, making the the squishies less so doesn’t exactly mean they’ll be incredibly durable. They will be durable enough, though, to discourage many of the early game shenanigans that make this game fun, particularly if they stack health. Imagine that you hit that level one Ashe at 15 percent reduced damage. If she gets any health beyond her base you will have a very tough time bringing her down unless you were annihilating her before this change.

The real problem, though, is for the tanks. Because of the way the new armor penetration works, tanks become essentially as squishy as everyone else as the game wears on. The only champions that won’t be affected as heavily will be tanks like Shen or hybrids like Garen, who have flat or percentage-based damage reduction with no counter. Effective HP tanks, tanks like Rammus and Mordekaiser, will have a very tough time against this change.

This change is also a nerf to caster damage. One of the best ways to currently improve caster damage is by purchasing early magic penetration. Magic penetration doesn’t scale per level as armor does, so players who don’t invest in MR items are highly vulnerable to magic attacks. With the new change, magic pen will be garbage against most targets, making pure AP the best way to go, which already scales fairly poorly if you can’t get fed.

Maybe the biggest problem with this change, even bigger than making tanks feel very obsolete, is the fact that this pushes people away from variety and toward sameness. HP is now so much better than MR or armor that most tanks will probably just stack it instead. DPS toons now have virtually zero incentive to choose an attack damage item that isn’t Infinity and an attack speed item that isn’t Last Whisper.

I’ll be playing a lot on the Test Realm to get a better sense of how this actually affects the game. In the meantime, enjoy your rune pages while you can and start saving IP for some new ones.