I play and build Vayne very differently in a Dominion Game in the Crystal Scar than I would in a normal game.

First of all, to play Vayne efficiently in Dominion, you have to take advantage of the environment. The Crystal Scar offers way more walls to impale your enemies into with your condemn skill than the summuner's rift. Based on this, I will present the build I use on Vayne in a dominion game.

Pros

• Has a nice stun
• High damage output
• Movement speed passive to catch up with enemies

Cons

• Squishy (so you need to be aware of your surroundings)
• Limited by it's range (no ultimate with infinite range to cancel enemies capturing)

Impaling your enemy into the wall with Condemn is key, by adding the damage from Condemn(+ impale bonus) and the damage output from regular attacks during the 1.5 seconds your enemy is stunned, chances are he is dead already.

That is why I max out Condemn first, it increases the damage dealt by the skill itself and the bonus damage from impaling your enemy and reduces its cooldown dramatically.

I use Greater Mark of Desolation and Greater Quintessence of Desolation because they increase both the auto-attack damage and Condemn's damage. I also use flat armor Greater Seal of Armor and flat MR Greater Glyph of Magic Resist. I prefer always using primary runes for every type as it gives me the best overall stats, also since I do not build any defensive items the armor and MR from my runes and masteries help a lot.

Ghost is a must in my opinion in dominion. I use Garrison as second summoner spell because I find it really helpful in many situations, as it can be used while you defend a point as well as when you engage a point.

Exhaust could also be a good choice. Really helpful against heavy dps champions.

Ignite is a bad choice for Vayne because she does not need the extra damage from ignite. It would only become useful against heavy life steal champions or healers (because ignite reduces by 50% the health received, something many people forget). But still, Garrison and Exhaust are much better choices.

Flash isn't really helpful to escape since it was nerfed, the walls in dominion are often too thick to flash though them.

-- Early Game --

Prospector's Blade

This item gives you a huge boost early game to win the first fights and you will almost never reach a point where you need to sell it to make room in your item slots.

Boots of Swiftness

Boots are a personal preference really, I prefer Boots of Swiftness but I still try berseker's boots from time to time to try and see which one works the best.

-- Mid Game --

The Lightbringer

This dominion-only item is really useful to Vayne for many reasons. It grants you vision of the enemies you hit for a few seconds. This is REALLY useful when an enemy runs around a corner or into a bush trying to escape, or for champions like Wukong who go stealth. Also, as you use Condemn really often to impale your enemies, you will often throw them into bushes and The Lightbringer will let you continue to shoot them without entering the bush!

I also like Phage a lot since it gives me just a little more health to help me survive some situations. The slow is also really useful.

--Late Game--

Late game items depend on the game, if you are facing heavy armors, focus on armor penetration items like Last Whisper, if you are facing high dodge enemies like Jax (which you will face quite often in dominion) then the Sword of Divine comes in very handy (its ACTIVE makes sure your attacks are never dodged). The Sanguine Blade and Infinity Edge are also good choices, but keep in mind that life steal is not what will keep you alive through a fight. This is why I do not build any life steal items until very late game.

I also tend to focus on AD items rather than critical strike items simply because the damage of Tumble and Condemn scales on your AD and not on your critical rate.

I am still trying different late game items and hoping to receive suggestions in comments below.

-- Use the jungle --

I will not go into the whole "how to play dominion" because everyone has different ideas about that, but I will just say that I find vayne really efficient in the middle jungle, ready to jump on an enemy trying to capture one of your point. You can also ambush enemies from the many bushes. In short: stay close to walls since you need them to kill enemies and survive. Staying in the jungle also makes it easy for you to take the health packs, they are key to your sustainability.

Staying in the middle jungle also keeps the other team wondering where you are and let's you take the middle buff as soon as it's up without wasting time to get there.

You will have hard time fighting against 2 enemies but in a 1v1, if you manage to impale your enemy with Condemn you will win. Against a tank you might need to run around while your Condemn comes back and impale him a second time.

Also note that you do not want to engage a fight under a capture point without someone to tank the damage.

-- Laning --

I realised Vayne really struggles in laning (especially the bottom lane) as while you are laning/pushing minions, you lose all the effect of surprise that you need to use Condemn properly. And since you are squishy, most champions jumping on you while you are pushing will crush you. That means you have to be very careful while pushing a lane and you must avoid pushing bot.

-- Use the mini-map --

In dominion the mini-map offers a lot of vision as you have vision on every capture point, on the center of the Crystal Scar and on all your team members. I will not waste too much time explaining why the mini-map is important because it is pretty obvious but ss Vayne (or as any champion...) you will benefit a lot from using this mini-map. You can usually spot your enemies as they go for undefended capture points and cut them off and surprise them ( don't forget : surprise = Condemn lands = enemy dead).

In conclusion, the Crystal Scar offers a whole new map and it changes a whole lot of things for Vayne. I presented here the build I find fits the way I play vayne in dominion.

Landing a good Condemn is the key to victory! But it requires some skill, strategy and timing.

Feel free to give me suggestions so I can improve this guide.

Nov 24th 2011:
-Updated to the new Mastery Tree (Season 2 update)
-Added section on mini-map

Nov 24th 2011:
-Changed items, added Phage as early item.