I want you to try a little something for me.
Take a look at your hat. The thing on your head, whatever it is. Engineering goggles, part of your T5 set, perhaps the Brutal Gladiator helm.
Take a good long look at it.
See that meta-gem socket? Have a peek at that.
What’s in it? What is socketed there?
If you answered anything besides “Chaotic Skyfire Diamond” go stand over there.
CSD is also an acceptable answer. 
Ok, now, IF you are standing in the corner, here is a 24 pound frozen catfish. Take this fish, and HIT YOURSELF AS HARD AS YOU CAN IN THE FACE.
Now, go sell that fish, and go buy the meta-gem you’re supposed to be using.
Chaotic Skyfire Diamond
There really is no reason you should not be using this meta gem, no matter what you’re doing in WoW. Whether your in high end raiding, end bracket PvP, or just starting out Karazhan, this thing should be slotted. No exceptions. Nope, not even then. Or then.
I surely don’t need to spell this out. This is the best meta gem in existence for mages. That is, until they come up with something that, on successful Ice Lance, “turns your opponent into a blithering idiot that takes 6000% damage from all abilities”.
The +12 spell critical strike rating isn’t, really, what’s important here. It’s nice, but largely forgettable. What we’re really interested in is the 3% Increased Critical Damage.
Pay attention to that. A 3% increase, not to bonus critical damage, but the entire critical strike. Meaning that the gem is affected, and amplified, by talents.
I can haz math?
Let’s assume a spell that hits for 1000. Let’s say it’s an arcane spell; I’ll call it “Frank”.
So Frank hits for 1000 damage, and crits for 1500 damage. This gem would therefore increase the critical strike damage to 1545 damage.
1500*1.03 = 1545
Throw in Spell Power which increases the critical strike damage bonus by 50%. Frank now crits for 1750 damage.
Now let’s add in the CSD. It increases critical strike damage by 3%, therefore:
1750*1.03 = 1802.5
Right?
Wrong.
See, what actually happens is a wee bit more complicated, because that’s just how Blizzard rolls.
Go back to the previous number, 1545 damage. The CSD’s multiplier is applied before any critical strike damage bonuses are applied. Split the 1545 critical strike into it’s… hmm, I’ll call them components.
Look at the spell this way: 1000 damage + 545 critical damage. The 1.5 modifier from Spell Power is applied to the CSD modified 545 damage, thus:
545*1.5 = 817.5
Therefore Frank would actually critically strike for 1817.5 damage.
So let’s take this over to the frost tree, utilizing Ice Shards. I’ll call this spell “Fred”.
Fred is exactly like Frank, except it’s a frost spell rather than arcane. Fred hits for 1000 damage, and crits for 2000 damage thanks to the sheer awesome that is Ice Shards. Split the spell into it’s components, and apply CSD’s effect…
1000 regular damage, 500 damage regular critical strike.
500*1.03 = 545
545*2.00 = 1090
Therefore, Fred will critically strike for 2090 damage.
Awesome? Why yes, yes it is.
I can haz PvP?
So why is it so good for PvP, some of you may ask. After all, you may say things like “Pfah, this here is PvP, you don’t crit often enough for this to be worth it, what with resilience and all.”
Ahh, but you see, that’s exactly the point. Part of resilience’s effect is to reduce the damage taken by critical strikes. And what does the CSD do? Why, the exact opposite.
Effectively, CSD negates resilience. Yeak, I know, I know, “wait… what?” was my initial reaction, too.
Resilience used to work exactly like CSD works (as, hopefully, explained above). Now, however, resilience merely applies simplistically to the final spell.
Take frostbolt… I mean, Fred, and whatever Fred is being fired at has enough resilience to reduce the damage taken from critical strikes by 15%.
Fred (without CSD) critically strikes for 2000 damage. Only 85% of the critical strike would actually count, thus…
2000*0.85 = 1700
Socket up the CSD…
2090*0.85 = 1776.5
76.5/2000 = 0.03825
The CSD has effectively negated 3.825% of your opponent’s critical strike damage mitigation.
It takes 19.7 points of resilience at level 70 to get a 1% reduction in critical strike damage.
19.7*3.825 = 75.35
Thus, by equipping the CSD, you are effectively negating 75.35 points of resilience on your opponent, as far as critical strike damage is concerned.
And that is, by no means, a small number.
Not convinced yet?
Darth Vader approves of the Chaotic Skyfire Diamond.
[...] further maths, see this post here about the [...]
Yes! Yes! Yes!
I took a close look and I’m a proud owner of a CSD, which I’ve been wearing since last autumn when I got the T4 helm.
It’s really about time I switch the head. But the gem will definitly be CSD. I wouldn’t dare to disobay the orders from Euripedes, would I?
You are a bit off dude. You are using a huge assumption on the 2nd bonus to that diamond. You assumed that it refers to spell damage. it **DOES NOT**
I was completely confused on the CSD, but there is a post in the forums that spell it out cut and dry.
http://forums.wow-europe.com/thread.html?topicId=1016252493&sid=1
Your math fails.
cheers mate
nice post euri. You MIGHT have convinced me to replace my 18stam and 5% stun resist gem in my pvp gear with a CSD.
then again, 18 stam and 5% stun resist is nice.
Hamanoptera. ummm. I do believe you are mistaken and would do well to check your facts. You appear to be referring to a completely different gem which is thus completely irrelevant.
The chaotic skyfire diamond does exactly what the OP says, and you have linked a post about a relentless earthstorm diamond, which does something completely different, as one might expect, being a completely different gem.
BUT WHAT ABOUT MY STUN RESIST OMIGOD !
@ Hamonaptra
Your a little behind the times (a year to be precise), and got the wrong meta gem to boot.
The Relentless Earthstorm Diamond originally did precisely what the CSD now does. It initially only applied to physical damage, but was changed in patch 2.1.2 to apply to all types of damage.
Patch 2.2 reverted it back to physical damage.
And then the CSD was created.
Which applies to spell damage.
Wrong gem, Hamonaptra. Quite possibly the greatest fail I’ve encountered on a blog in my life.
Wake up, silly.
yeah…. who knows WoW math better….Euri or god?
…trick question …Euri IS god when it comes to WoW math !
and i have had a CSD since they have been around
Uhm did you use a calculator to calculate 500*1.03=545?
If yes, I kindly recommend to take the caculator and sell it together with your fish to buy a new, working calculator.
500*1.03=515 and 515*2 is 1030 thus you crit for 2030 on a frostbolt. Thats a ~ 1.5% damage increase instead of the 4.3% increase you have calculated. I dunno if the other gems are actually better, because I’m too lazy to calculate it right now, but you sir Fail.
Ok… If you assume that you crit 1 out of 3 attempts effectively, weather in PvP or in PvE a 14 SD meta will actually give you 12.74 more damage on your frostbolt, if you talent for it.
So in 3 hits it will give you 4 times (2 hits and one crit that will be looked at as 2 hits) 12.74 damage more (~51) while the CSD will give you like 1.5% more damage on one hit. For me (986 SD), this is 48 damage, so with frost, especially in arena I’d take the 14 SD gem over CSD. With firespells in a raidbuffed situation and farm more SD and thus higher crits, a percentual amount will outweight the 14 SD easily, simply cuz with the firespells you will get 2.1% more dmage out of your crits due to ignite. Since the damage you gain from those 2.1% is even more in that situation, 14 SD will fall behind.
Do your homework before recommending ppl to mindlessly change metas.