This is my first guide so apologies if I sound "noobish" in any way or make a general mistake. Please just post in the comments and I'll update it.

Veigar has amazing burst. That's why. I enjoy playing Veigar, because he has so many different ways to build and still be incredibly fun and bursty. So you could have a high survivability Veigar, while also having a high burst Veigar.

The reason I chose these runes is to make Veigar even more bursty at level 18, but also still have some magic Pen from the marks.

I went with the items in this build for one reason only burst, mixed with a small amount of survivability. You want to start off with the Prospector's Ring. Why you ask? Because it adds some health a decent amount of Ability Power, and most important some mana regen. Then going down the list, Sorcerers shoes for magic Pen and speed, Morello's for Cooldown Reduction, a good bit of AP, and some Mana regen. I then went with Deathfire Grasp, because it helps a lot with Veigars burst. Lch Bane for the amazing proc, and slightly higher move speed, and then Deathcap because AMG AP. After you get this if the match isn't over yet, sell off your prospecters ring and pick up Zhonya's. It's a life saver.

When you get into a team fight, you have to remember one thing. Veigar does not have sustained damage. He is bursty, but when you release your burst, back off a bit, and simply stun, q, and w, Until you get your ult back then get up in their faces.

When you are 1v1, it is important to remember you are super squish. Try to run away whilst dropping Event Horizon behind you. If they get caught, quickly throw out Dark matter, and then Baleful strike and your ult if it's up. If not that should be enough to get them to back off.

I'll finish writing more on this later, and will update it daily as I receive comments. I am also going to be putting some videos up for everyone to watch as to how I work Veigar.