Pros

• Very powerful mid to late game.
• Fun to play
• Has a True Damage ability Silver Bolts that makes stacking armor against you almost useless.

Cons

• Very squishy and somewhat weak early game.
• Does not have any life-saving escape abilities.( Tumble wont save you from a chase/gank)
• Requires time and skill to master.
• Easily shut down with a single stun or blind.

The world is not always as civilized as people might think. There are still those who would follow the blackest paths of magic and become corrupted by the darker powers that flow through Runeterra. Shauna Vayne knows this fact well. As a young privileged girl in the heart of Demacia's elite, her father tried to convince her of the constabulary's ever-vigilant eye. Young and naïve, she truly believed that her world was one of perfect safety... until one night, when a twisted witch took interest in her father. The malevolent woman overcame her father's conciliar guard, then tortured her family before murdering them. The young Shauna escaped only by hiding herself and then fleeing once the hag had departed, plagued by the screams of her loved ones as she ran. A burning hatred was born in her that day, one that could never be denied.
Vayne was able to take care of herself using her father's money, and she began to train as soon as an instructor would have her as a student. By the time she was a fully grown woman, she had become a grim warrior. However, the fields of battle were not to be her home. Demacia needed a protector, one who hunted those lost to the darkness. Shauna used her family's contacts to become the first Night Hunter, and now her prowess is the stuff of legends. It is said that those who practice the black arts quake when they hear that the Night Hunter is on the prowl. Despite her crusade, Shauna has looked at the League of Legends in horror. There are champions who have clearly lost themselves to the blackest of magics, and who have been embraced within the League even though they should be put down for the safety of all. The time has come for the Night Hunter to execute her secret mission – to purge the League of Legends.

"Not all shadows are to be feared. At least, if Vayne has her way."

The ones I use:

In this build, Vayne is all about who you're matched up against and what lane you are in.
MIDDLE LANE:
This is the lane in which I play Vayne most often. She is a very good 1v1 but she isn't good against 2 people, even if it's 2v2. In middle lane, you want to play passively until you reach 6-9 or until you get most of your Phantom Dancer ( Zeal and Dagger). Then you should start playing agressive, but not by harassing, but by getting out a good combo of 3-6 shots. Remember, you want them to think that most of your damage is coming from your q, Tumble because that is normally where all the damage from Vayne comes from. Your standard combo should be something like this: r+q+auto-atk+auto-atk+auto-atk+auto-atk+auto-atk+auto-atk and so on untill you kill. It should take very few hits if you're against someone like Ashe.

Follow what is on the cheat sheet OR:

Upon selection
"Let us hunt those who have fallen to darkness."
Attacking
"I release them from their pain."
"I bring swift death."
"They will be purified."
"Cleansing blood with silver."
"I pass judgement."
Movement
"On wings of night."
"The shadows are to be feared."
"The dark should fear me."
"I hear the innocent cry out."
"I smell black magics."
"In the dark all is laid bare."
"Evil lurks around every corner."
"Beware!"
Upon learning Silver Bolts
"Silver of the moon."
"The purifying element."
"Purged with silver."
Upon activating Final Hour
"Time for reckoning."
"The die is cast..."
"Impure fools."
Taunt
"Hitting me is like boxing with shadows."
Joke
"Joke? What do you mean?"
"I have no time for nonsense."