WARNING: These masteries are still using the old tree and have not been updated to the new tree by the guide author. As such, they will be different than the masteries you see in-game.
In my last version of this guide, Riven was too tanky with not enough damage. In this new revamped version, she has less health, but still the same amount of defense, and also much more damage. Also, while building more damage, the stun will be stronger and the shield will be bigger. The skill sequence has also been changed, maxing Ki Burst and Valor before Broken Wings. Doing this will help a lot in duels with the longer stun and bigger shield.
I have played Riven for quite some time now, and thought that the previous version of this guide was the best. Now that I have entered a high-elo environment, I needed more damage. While sacrificing some health, the new Riven build incorporates the ability to do TONS OF DAMAGE and still take some hits.
Here's my Penta with Riven:
(Don't pay attention to the build; it sucks alot)
Items
The new item choices aim to deal out more damage. 2 The Bloodthirster and a Guardian Angel allow you to deal quite the amount of damage, and coming back instantly to deal even more, or s W, E, and Q to safety. An early Guardian Angel is vital, for it can help absorb damage in laning duels and bring you back to win the fight. Adding a Last Whisper at the end of the build can counter opponents building armor. Guardian Angel, in addition with aegis of legion, give you some tankiness to survive in teamfights.
Some items to substitute or buy-and-sell:
Early:
Two Doran's Blades can give you an extra bit of health, lifesteal, and AD if you're not doing too hot (which you shouldn't be).
Buying The Brutalizer before your The Bloodthirster is all up to the situation and what you want to do. If you are laning against a low-armor opponent, this is recommended, but if not, skip this.
Mid Game:
This is a great item against CC heavy teams. Using it can let you Q to safety or chase a target attempting to kite you.
Late Game:
Building a Last Whisper instead of a 2nd The Bloodthirster paves the way to building these two items. A Maw of Malmortius is a great item on Riven. It adds AD, MR, and a passive that can save you from a Karthus or Ezreal ult. Randuin's Omen is an amazing item on Riven. Its passive helps you win duels against those fed AD carries, and its active is pretty much an Exhaust.
Ignite is a good at finishing off enemies, but is somewhat unreliable. Using it in duels to deal constant damage over time can help burst people down, and your opposition will be even lower if you need to Flash-chase.
Flash is one of the best two-way moves. It can be used to get away or chase and dive turrets.
Teleport, even though most solo-tops use it, is not useful to me. Riven is a high-mobility champion that can get back to lane just as fast, and since you will be dominating them, you will not need to worry about them pushing.
Exhaust can be used for the same purpose as Ignite, but with a different effect. In duels, you could use this spell to reduce their damage output, but killing them faster is way more important.
Skill Sequence
Runic Blade Passive: Riven's abilities charge her blade, causing her to do 5 / 7 / 9 / 11 / 13 / 15 (+0.5 per bonus attack damage) bonus physical damage on her next autoattack. Riven can store up to 3 charges, and will only expend one at a time.
This passive is crucial in duels. Using it separates the good Riven players from the bad ones.
It adds a lot of AD to your basic attacks after using an ability. Spacing your abilities out and basic attacking in between will show many results.
Broken Wings - Q Riven steps forward and lashes out in a series of powerful sword slashes that will damage all enemies nearby. This ability can be activated a second time within 4 seconds, and a third time within 4 seconds of that. On the third activation she will also knock nearby enemies back and have a larger radius of damage. All three strikes will deal the same amount of damage. Physical Damage Per Strike: 30 / 55 / 80 / 105 / 130 (+0.7 per bonus attack damage) Total Physical Damage: 90 / 165 / 240 / 315 / 390 (+2.1 per bonus attack damage) No cost Cooldown: 13 seconds Range of dash: 260 Diameter of damaging AoE: 225 Diameter of third strike's damaging AoE: 300 Knockback: 225
This ability is a three part attack/retreat move. Using basic attacks in between Broken Wings activations will add a lot of burst to your attacks.
Ki Burst - W Riven deals physical damage and stuns nearby enemies for 0.75 seconds. No cost Diameter of AoE: 250 Cooldown: 11 / 10 / 9 / 8 / 7 seconds Physical Damage: 50 / 80 / 110 / 140 / 170 (+1.0 per bonus attack damage)
This ability is your main tool of harassment. Max this first. To harass, E towards them, autoattack, W, then Q away. If you think you can finish them, Q towards them and autoattack in between activations for maximum damage output.
Valor - E Riven dashes towards the cursor and gains a shield for up to 2.5 seconds. No cost Range of dash: 325 Cooldown: 10 / 9 / 8 / 7 / 6 seconds Shield Strength: 60 / 90 / 120 / 150 / 180 (+1.0 per bonus attack damage)
This move and Broken Wings are what makes Riven a high-mobility champion. This move can decide a win or loss in a duel. the extra damage that you can absorb and the proct of Runic Blade can win any close duel.
Blade of the Exile Riven's sword reforms, gaining 20% bonus attack damage, extended range on her damaging abilities and autoattacks for 15 seconds. She is also granted the ability to use Wind Slash once for the duration. Cooldown: 75 / 60 / 45 seconds
Riven's ult is obviously the best "passive-like" ult in the game(yes, even better than Jax's). More AD, and extended range on her abilities plus autoattacks is great. Use this against a fed opponent or to just utterly destroy someone.
wind slash Wind Slash Riven can activate the ability to emit a shockwave in a long cone in front of her that deals physical damage to all units hit based on their missing health. No cost Range: 900 Missile speed: 2200 Bonus autoattack range: 75 Bonus Ki Burst range: 20 Broken Wings new AoE: 325 Minimum Damage: 80 / 120 / 160 (+0.6 per bonus attack damage) Maximum Damage (25% health or lower): 240 / 360 / 480 (+1.8 per bonus attack damage)
This is the guarantee that no one will ever escape your grasp. This cone-skillshot nuke can always get you the kill on opponents with less than 25% health.
Summary
Riven is a great character that is easy to grasp but takes time to master. She has a great early laning phase, mid game, but her damage falls off a bit if your The Bloodthirster stacks are not maxed.
Pros:
High Damage
High Mobility
Strong All Game
Safe to Pick in Blind, No Hard Counters
Difficult to Gank
Extremely Fun to Play
Versatile; Can Be Played Top and Jungle
Not very Tanky
Damage Falls Off a Bit Late Game
Can Be Kited by Certain Charaters
Build Guide
Discussion (1)
The Bloodthirster and a 
Guardian Angel allow you to deal quite the amount of damage, and coming back instantly to deal even more, or s W, E, and Q to safety. An early 
Last Whisper at the end of the build can counter opponents building armor. 
Exhaust.
Wind Slash
