There isn't an item slot for it yet, but augment to either death(recommened) or power whenever you feel it is need. I have heard about its price dropping to around 1000, so it won't be as expensive. it's not as important as a main item, but important none the less.

Hey, my name, is unimportant(if you must know, just ask). What IS important is that I bring you a bite-sized guide that will surely help you destroy the competion. Viktor is no assasin, but build him right and he will be a very tanky(and very powerful) mage. Also, his dance is OP, just saying. this guide lives by his saying "with utmost efficiency", and will be deceptively short.

I tend to take ignite and flash, as they are good in almost any situation, with any character. You can also take teleport and flash, and if you like going mid as much as I do, teleport can be invaluble.

If you can pull it off, the extra armour from power transfer can save your life, use it well, and don't forget it has a short cooldown.

Death ray. well, the name says it all. If the two clicks are scaring you, don't worry, it's just click, drag, release. because you can start it anywhere in the circle, you can place it on the edge and get a fairly long-range skill shot. keep in mid it has around an 8-15 second cooldown. aiming across lines minions is really fun and effective. it is also AoE which is nice. Also, pick up some nice fog of war kills too.

Gravity field. I wouldn't rely on it too heavily. fairly long cast time and not immediate stun make it only really useful in team fights when everything is crazy.

Chaos storm. It moves slower the farther it is from you, so don't expect it to chase down your foes. it is very very powerful for clean up and mop up any stragglers quite nicely. it also looks scary, and intimidation is a large part to this game.

On a final note, he isn't leblanc, don't expect him to take half the enemy health, but expect som substantial damage.

I worked it out and, with your masteries, you could have 30 ap ant level one with no help from items whatsoever(and your doran's ring will help nicely afterward). the magic penetration does crazy damage early on when they have only default magic resistance to aid them. mana regen, always important.

In short(very short, at this point) Viktor can be invaluable, even when you already have a mage, just make sure that your team is spread out nicely, if you already have four ap guys, please use an ad character. He isn't an assasin, but he's darn strong and and take a bruising. also he's Russian, you can't beat Russian.

Any inquiries or need for more info, please comment, I'll try to get back sooner rather than later, though I can't promise if this guide is a getting on in age.