Runes: +AP/Level vs Magic Penetration

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Octovert

Senior Member

10-08-2009

When placing blue runes, which do you favor and why?


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Khrane

The Council

10-08-2009

The way I see blue runes for casters, the three stats you need are AP, Magic Pen, and CD reduction.

The easiest of these to obtain with items is AP, followed by CD reduction, then magic penetration.

So... It depends. I think that AP isn't the best for anyone because you can get that so easily in-game. If your hero's item build is able to incorporate CD reduction easily, then stack penetration. If your hero would be better off not getting CD reduction, and instead is able to get an abyssal scepter sometime... Get CD reduction.

IMO


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toomad

Senior Member

10-08-2009

CD reduction gives the highest dps increase over time, but that comes with increased cost and the spells won't hit harder.

AP is straight forward linear dmg increase.

Magic penetration is best for champions that only have nukes (doesn't improve heal and ultimate of taric for example) and it's a % increase in dmg not linear like AP.

Conclusion:

CD reduction is great for spells like hate spike (q skill) of Evelynn or to reduce high cooldowns and/or if you have enough mana (regen) to keep the spells spamming.

AP is best if you want to boost base damage, spells with high AP ratios and for champions that not only have nukes (other not offensive spells that benefit from AP)

Magic penetration is best for characters like ryze or annie later in the game when they have higher AP. Penetration becomes better the higher your AP (or the spells damage) is and worse with smaller numbers (% increase!)


I hope helped.


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Roadkill

Senior Member

10-08-2009

You really need to do the math, and figure out which is better. It's complicated because AP (typically) affects damage whereas magic penetration (MP) affects magic resistance (MR). So it's a sliding scale - do you expect people to pick up MR items against you? How much?

For example, I ran the numbers on Veigar and found that the difference between AP and MR is minimal - MR only starts being more effective when the enemy has < 100 MR, and even then the difference is only a few points of damage. Therefore, it was better to take AP, because then Veigar could farm better with Dark Matter (since minions don't have MR).

I would say that if your AP-scaling ability is >= .8, then AP is probably a better choice. Otherwise MP will help more, even when the enemy has a high level of MR.


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Nullname

Junior Member

10-08-2009

As a rule of thumb take Magic Penetration


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Rudeboymike

Senior Member

10-08-2009

i think a better question is:

How much magic pen is too much?

The average resist for a champ is around 30-40 at 18, right?

Well you 15% off from masteries, maybe some from items, and then the rest is flat rate.

For the most part, if im using any AP build character, i stack all Magic Pen unless CD reduc is necessary (ie Morgana)


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Khrane

The Council

10-08-2009

Quote:
Originally Posted by Rudeboymike View Post
i think a better question is:

How much magic pen is too much?

The average resist for a champ is around 30-40 at 18, right?

Well you 15% off from masteries, maybe some from items, and then the rest is flat rate.

For the most part, if im using any AP build character, i stack all Magic Pen unless CD reduc is necessary (ie Morgana)
I think it depends on your team setup, also. If you have some major casters, the enemies are more likely to stack MR. Even with just natural MR+Mercury's Treads, you probably wont hit 0 with the mastery and runes. Abyssal Scepter might, though...


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Danulas

Senior Member

10-08-2009

I prefer AP because starting the game with over 20 AP (not including items that I can get at the start) can be pretty devastating to the other team.

Whenever I build rune pages, it's to give my champ an advantage early game. Items get me what I need for late game.


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Quinnister

Senior Member

10-08-2009

-CD% reduction is a great one to take, overall. I cannot think of a single downside to that.

Magic Pen vs. AP is a much better discussion. At the bare minimum, a champion will have 30 MR. With Archaic Knowledge, 15% of this is knocked off. Using your glyphs and quints, you can achieve a 12 spell penetration from your runes.

(100/130) - (100/((100) + (30-12)*0.85)) should model the % of damage you could expect to do more against a base level magic resistance. Basically, a 9.8% difference. By comparison, if they buy a 50 MR item, the difference changes to (100/180) - (100/((100) + (80-12)*0.85)) or 7.8%. Either way, it is a solid damage increase overall. For reference, this means 1000 burst magic damage results in 78 more damage.

AP, on the other hand, would increase the damage directly. Our spell damage would deal more damage against their base (100/100 + (30*0.85)) damage reducer.

Working off the best possible case for magic penetration, let's suppose our spell does 300 damage normally but we have an extra 51 AP (the amount of AP from glyphs and quints at lv18).

1:1 ratio
300 * (100/130) = 230 base damage
351 * (100/(100 + (30*0.85))) = 279 damage
300 * (100/((100) + (30-12)*0.85)) = 260 damage

750 * (100/130) = 577 base damage
801* (100/(100 + (30*0.85))) = 638 damage
750* (100/((100) + (30-12)*0.85)) = 650 damage

As you can see, AP does better at lower damages however spell penetration does more at higher damages. Either way, the difference is slight. If your AP ratio is lower than 1, spell penetration has a larger advantage. As the enemy stacks MR, AP has a larger advantage.

However, if -CD lets you spam one more spell than these other ones, -CD becomes the victor.

It's all a matter of taste because each has its own purposes.


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Octovert

Senior Member

10-08-2009

Wow. This is so much more detailed information than I ever expected from this post. It sure doesn't seem like it matters much at all, really. I'll probably stick to the AP just because I don't meleve MP can reduce a target below 0 MR, and thus AP will be more effective against creeps.


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