Howdy folks!



Let's discuss Challenge Rating and gameplay! Fun-ness abounds.



Challenge Rating affects the following stats:

Armor, Armor Penetration, Critical Hit Rating, Critical Damage Rating, Critical Resistance, Block Proficiency, Block Penetration



What Does CR do?



Challenge Rating doesn't really have a direct comparison of values. There's no way to say "10 Challenge rating equals -5% Armor Rating". But, I'll do my best to explain the scale and how the stats work. Buckle up everyone!



All stats listed go through the same formula (except for Critical Damage Rating that uses a similar formula with a couple of extra steps) and that formula is this:

(Player Crit Rating / [(5 * Opponent Challenge Rating) + Player Crit Rating + 1500))



All of the stats use this formula to turn the rating that you see into a percentage that's used by the game calculations. As an example, Armor Rating turns into Damage Reduction once it's gone through the formula. Here's a few examples to showcase how Challenge Rating affects that value.



How Much Does Challenge Rating Affect Stats

-TL;DR - Roughly 1-2.5% relative power is lost or gained per 10 challenge rating.



Opponent Challenge Rating = 80 || Player Armor Rating = 1200

(1200 / [(5 * 80) + 1200 + 1500)) = 0.3871 or 38.71% Damage Reduction



Opponent Challenge Rating = 100 || Player Armor Rating = 1200

(1200 / [(5 * 100) + 1200 + 1500)) = 0.375 or 37.5% Damage Reduction

--Relative drop from 38.71 to 37.5 is a relative drop of about 4.5%



Opponent Challenge Rating = 120 || Player Armor Rating = 1200

(1200 / [(5 * 120) + 1200 + 1500)) = 0.3636 or 36.36% Damage Reduction

--Relative drop from 38.71 to 36.36 is a relative drop of about 6.5%



Keep in mind that the power drop or increase is relative. A champion that boasts 50% Damage Reduction will see a larger drop than a champion that only has 10% Damage Reduction.



1 - 2.5% Relative Power decrease? How much is that in realistic terms?



Well, that's where things start to get very difficult, but I'll try my best. Please keep in mind that I'm a Dev, not a community person, so my explanation skills can be a bit sub-par at times.



Let's imagine that you had a champion that had 10,000 Health. You had two options for a Mastery. One increases your Health by 7,000 and the other increases your Damage Reduction by 50%. Which is better? That's where the concept of Effective Health comes in.



If you take the Health increase, your effective health rises to 17,000 (10,000 + 7,000 - makes sense), but the Damage Reduction Mastery actually increases your effective health to 20,000. If you have 50% Damage Reduction, all attacks deal half as much damage, which means that your health has effectively doubled because it takes twice as many attacks in a fight to knock you out.



Effective Health Calculation looks like this, for any fellow RPG nerds out there:

Effective Health = Health / (1 - Damage Reduction)



So what does that mean for our relative power decrease from above?



Well, most Champions in MCOC float around 20% Damage Reduction (this number fluctuates quite a lot between champs and abilities, but 20% is the closest to an "average" that exists). Let's see how much Health is lost with a decrease from above:



Damage Reduction 20% || Opponent CR 80 || 10,000 Health

10,000 / (1 - 0.2) = 12,500



Damage Reduction 19.6% || Opponent CR 90 || 10,000 Health (2% Relative Power Drop)

10,000 / (1 - 0.196) = 12,437



Overall, after all is said and done, you lose or gain roughly 1% effective health for every 10 challenge rating. Now, keep in mind that this is a single example in isolation. Once you get out into the game and you start adding Armor, Resistances, Block Proficiency and about a hundred different abilities, masteries, nodes and boosts flying all over the place, the calculations get a little more tricky.



What Else Does Challenge Rating Affect?



Apart from stat scaling for the above listed stats, nothing. It doesn't affect Ability Accuracy or Proc Chance for abilities. It doesn't affect who has priority for an attack or any other non-stats mechanics in the game. I even had the engineer go through the code to make 100% sure this was the case before I answered this question.



What Does each stat do once it's been turned into a percentage?



Armor, Block Proficiency, Physical Resist, Energy Resist - Damage Reduction. Percentage of the damage that is reduced from incoming attacks



Crit Rating - Percentage chance to score a critical hit



Crit Damage Rating - Percentage that your damage is multiplied by when a critical hit is scored.



Armor Pen, Block Pen, Crit Resist - How much of the opponent's stat is ignored

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