Hey guys. this is my build for viegar. ive been working on this for about a month, trying to work out the kinks. and im thinking i got it down. Please leave constructive comments! Sorry but this is gonna be a pretty low tech guide. just straight words for now.

this is the biggest game changing category for the wise viegar player!

GREATER QUINTESSENCE OF INSIGHT
this gives you some extra penetration to take out the foe a lot quicker.

GREATER MARK OF INSIGHT
this gives you, yet again for more punch. with these 2 alone, you should be hitting hard enough to make any enemy cringe in fear!

GREATER SEAL OF KNOWLEDGE
this gives you more mana to keep those baleful strikes rolling!

GREATER GLYPH OF FOCUS
this combines perfectly with the seals of knowledge! you have the mana to support you baleful strikes, and now you can pump them out even faster!

This is pretty self explanatory with the summoner spell ive shown. you have the 9 points in offense to give you the extra penetration it offers. you also have a large array of utility masteries to give you movement, experience, extra clarity/ghost, as well as mana.

alright. ive benn looking at the comments below and exploring some of the options. ive found that the best way to have the survivability i personally like and add some more nuke power is to rush a WotA. after you have that, go into your ever reliable sorc shoes. the next thing i would go for would be the deathfire grasp. the mana regen is great to have. the trick though is getting used to using the item from your inventory like an ability. the next item i build is great in my opinion. ive been using this for some of my other AP characters and after really looking at it, i cant believe i havent been using it for Viegar. the void staff is a great item for magic pen. it gives all of your spells so much more punch its not even funny. the last 2 items are pretty standard AP. build them in whatever order you please. i like building lich bane first simply cause you have a bit more space in your inventory to work with.

this is a weirder spread sequence. i get all 3 within the first 3 level because it helps to have all 3 working in a combo. outside of that, start pumping points into baleful strike. you may notic i stopped before hitting level 5 strike. that is because by the end of rank 4, you should be able to one hit minions. that means you can still build AP even if you put another point into dark matter. then you build up to rank 5, proceed with dark matter, but at some point, you will want to put an extra point into event horizon just so you get the stun length. there is a big combination effect with viegar.
it goes something like this:
EVENT HORIZON->DARK MATTER->BALEFUL STRIKE/PRIMORDIAL BURST
the slash is in there because the combo depends on if you are pegging champions or minion waves.

Pretty Straight forward. but im gonna state why just in case. you want CLARITY for the mana early game. it also helps you partner out if they are running low. use GHOST for your escapes and chases. remember to use EVENT HORIZON to help you both ways. Other good spells would be IGNITE and FLASH.

PROS:

Great stun
very effective gank late game
great for group fights
ultimate anticaster
Great skill Scaling

CONS:

Very Squishy early game
very mana hungry early game
easily ganked if not careful

Ok. im going to rephrase this due to some comments. I DO NOT RECOMMEND VIEGAR ENTERS THE JUNGLE AT ALL. the only reason you should be entering is if you are grabbing blue buff with the aid of your jungler or another champion. i am not saying that you should jungle him, he is in no way made for that.

when it comes to team play with a Viegar, i have found that the most important thing to do oddly enough is ignore who your team is targeting. shoot at the enemy caster instead as soon as possible. this could remove a person from the fight, either by killing them outright or simply causing enough damage that they have to leave the fight. a 5v5 suddenly becomes a 5v4 in your favor.

The most unique thing about Vieger is his Event Horizon skill. the simple fact is that being able to stun large groups of opponents is handy and very effective. that 1.5 seconds could be enough to take a person out of a team fight, or even enough to allow your entire group to escape/chase. there are not many champions that can claim that they can take all enemy champions out of play for a second. it also pins the entire enemy team in one area. thats why its so important to get at least one point in it early.

Hope this guide helps you along in your Viegar journey! he is a great champion and under-rated by most summoners. Hopefully, you will find as i have and see just how good he is! thanks again for the comments! ive tried to redesign the build from my earlier tankier viegar build. Thanks so much for the comments! i tried it your way and, while i prefer tankier viegar(sorry, im in truth a tanky guy) this build works very well and due to WotA you gain enough surviability in my opinion to be useful.