The point of this build is to get Veigar as much AP as humanly possible and be able to completely annihilate any and all AP champions (and several non AP) that the enemy team might have, EXPECIALLY Annie (Complete this build and you WILL oneshot any proper Annie build). The end result will be well over 1000 ap and beyond (if you farm properly and get 20 stacks on your Mejai's Soulstealer) which, when using the damage converter, will cause your ultimate to do 500 + 120% of your AP in base damage combined with 80% of the enemies AP... Definately a force to be reckoned with but also vulnerable, try not to run alone as this build is in fact fairly ally dependant. With this build even non-ap targets will crumble (I actually managed to oneshot an Ashe with said build and brought a tank to half life with a single spell)
The runes seem a little unorthadox yes, I can allready hear the screams of "WHY DON'T YOU HAVE AP RUNES!?!?!? NOOB!" as I type this, allow me to explain.
For seals I prefer cooldown, they are actually quite nice late game to get your ult back as soon as possible to bring down the next target. Maxing out your mana or mana regen is nice but come late game you will find that waiting for your spells leaves you FAR more vulnerable than you would like for your tastes
Marks I found that the magic penetration comes in handy, you reduce enemy magic resist with your void staff by 20, why not add an extra 8 and a half just in case you get those pesky "I walk away with 5 life left, ha" folk...
For glyphs I decided to bypass on the AP runes and focus on the mana regen, all too many a time have I run out of mana late game, I found these to bring that occassion down quite often, you can even exchange exhaust for clarity in summoner spells if it gets that bad.
Again as with the glyphs I bypassed the AP runes but this time I took a different route: Getting 3% additional movespeed (It doesn't seem like much but it's half a zeal which can and probably WILL make a difference) and another cooldown reduction, bringing the grand total, counting the 20 stacks on your Mejai's Soulstealer as well as the masteries, to, thats right, 40(.05)% at lvl 18! Comes in handy, trust me.
The whole reason why I chose absolutely NO AP runes is because the ammounts added are not NEARLY as beneficial as they could be to Veigar. Veigar is the only champion that has a roofless AP ammount so why waste runes getting about 20 extra AP when you could farm that in 5 minutes and have a 40% cooldown reduction rate, faster movespeed, and some nice healthy mana regen?
These are what I feel best suit Veigar in his voyage to the unknown, you cannot predict a blind pick team so it's best to be well rounded. Good enough to get you into fights and deal as much damage then hightail it when the enemies come to gank you.
The exp gets your rune bonuses faster
The quickness gets you in and out of fights just a little sooner
The flash reduction comes in handy sometimes
The gold helps your build, I mean, those things are expensive...
Overall they should be pretty straightforward. If not leave comments and I'll go a little more into detail on them
This build is designed to get you the HIGHEST possible AP for late game to make you the most DEVASTATING AP force to be reckoned with in LoL histoy, I have in fact achieved this build on more than one occassion and have gotten the full 20 stacks on my Mejai's Soulstealer and trust me is it ever worth it. In skype with 4 allies as soon as this build is complete they know it's GG and I have never lost once, even with 2 inhibitors down, when this build completed. It will ruin 5 peoples days like you wouldn't believe.
If you find this build lacking too heavily in mana you can trade out one Rabadons or your Zhonyas with an archangels staff. If you find that you die too often for a Mejai's Soulstealer to be usefull, get a Deathfire Grasp in it's place or even Archangel's Staff and replace your Sorcerer's Shoes for Lucidity Boots...
The skills are HOPEFULLY fairly straightforward, the whole purpose is to get your Q maxed ASAP for farming, you WANT that AP bonus as soon as possible, and to use it as often as possible. Forget harassing, leave that to your lanemate. Get the last shot with Q on all minions, try not to lane with farm-dependant champions and ask your lanemate if he will let you get it instead. killing 100 minions with your Q spell gives you 100 ap bonus and it is NOT that hard to do at all.
As for Dark Matter... I know it is SOOOO tempting to get an aoe that does that much damage maxed out as soon as possible but it is NOT worth it. In the end you loose valuable AP and mana. Save it for late game when you're more concerned with killing champions and pushing lane than you are minion farming.
You're AOE stun, this one is tricky to master sometimes as it has confused many new Veigar players. I will give a runthrough of what it will and will not do...
Stun any enemy that passes through it (going in or out)
Effect even stealth and "dashing" targets
Effect those teleporting in and out of it
Stun those allready inside it when placed
Stun the same target twice
Ignore Banshee's Veil like some aoe's
This spells "range" is actually a little farther than the circle suggests, the casting range effects where the CENTER of the circle will be, not the edge... If that enemy champion is just out of range of your Q then drop this to make them stop. As you level this skill its stun lasts longer and longer, at level 2 or 3 is as high as you need it for it to last longer than it takes your W to "proc" or "land" when casted. I make it level 3 just in case of those runners, you won't be able to drop it immediately if you're target was caught with one of those barely rings just out of range of your other spells. Also... here is a fun fact about Event Horizon, if you drop it so that the EDGE of the circle lands directly on top of the target, it will stun them immediately.
VS AKALI: If you find an akali, usually the first thing she does vs a Veigar (just so she's not oneshot) is either dashes to him immediately to try and burst him down, or drops a smoke THEN dashes. If you have a bush nearby try to get in it, when she drops the smoke, wait about a full second then drop your stun directly on top of it so she cannot escape and leave a nice little Dark Matter burst in the center, she will either take the damage and be hurt for you to use your ult and q, or she will take the stun and when her invis ends you can ult and q her then and drop W on yourself in case she tries to dash to you... Either way she will die or have to run.
This is where the fun comes in. You will do INTENSE ammounts of damage in VERY short ammounts of time and makes you early game anti-mage and late game anti-everything. Anything hit by this after your build is complete will be in a LOT of pain, doing up to 1800 damage minimum, the more AP they have the more you hit for and lets face it. If someones building a high-ap build their hitpoints go down a lot unless it's Singed or something. But even then let's use an intermediate Annie bot, usually getting 200-500 AP but for arguments sake lets stick with only 200.
Complete build you will have bare minimum no Q farms of about 1000 ap solid. That's 500+1200+160 which is 1860 damage so that is about 90% of annie bots life gone... Drop your Q and shes done. If you had dropped your stun and immediately casted R then Q then voiala, you have one dead Annie in aproximately .5 seconds, and they actually build HP items.
The exhaust can be exchanged with whatever you desire but I find myself fairly loving the flash to get in and out quickly, it helps a lot... If you find yourself too dependant on mana because your going trigger happy with your spells get clarity, or lane yourself with a Soraka.
This build is heavily team dependant in the sense that you cannot go 2v1 ever. You drop everything you have on one target and wait 10 seconds before you can do it again and are squishy as all hell. Work together and stick with an ally that can hopefully taunt or tank really well and you should be fine. Map awareness is key, make sure you know that there are no enemies behind you and you have a surefire route out before pushing a lane too hard. Never initiate, one bad place of a stun and poof, there goes 6 of your Mejai Soulstealer stacks and your 20% cooldown reduction and all that punch you have packed behind you goes to nil. If you can, convince your allies to wait till you arrive so you can get a kill or at the very least an assist. One assist = 1 stack on mejais.