Introduction
Hey, I'm Kman. I'm a veteran Riven player, having grabbed her on release and maining her since, I've seen a good variety of builds for her. This is my version of the old bruiser Riven builds that were used around the time of her release. To quickly explain why I use it is easy - games more often than not end up dragged on into late game. This build is for that, as late game, you can become completely unstoppable, quite easily. As you become so tanky, it is hard to be killed, and along side that, Riven still dishes out an immense amount of damage. Late game, you will be a massive compliment to your team, easily bringing won team fights and won games.
Keep reading, I'll do my best to explain further.
(Note: Forgive me for leaving out some things, such as links and images for items in my explanations - this is my first guide. I'll try my best to update soon if this guide is liked)
Riven's Abilities and Usage
Riven has an amazing kit. In this section, im going to list off her abilities, and explain the basics of using them to your advantage.
Passive - 
Runic Blade Riven's abilities charge her blade, giving you one stack of her passive. This passive grants bonus damage to auto attacks, and can stack up to a cap of three.
W - 
Ki Burst Riven emits a Ki burst, damaging and stunning nearby enemies. The stun lasts for about .75 seconds (Seems short, I know) but it is absolutely necessary in winning fights.
E - 
Valor Riven steps forward a short distance and blocks incoming attacks. This ability is Riven's shield/Dash. This shield will be larger with the more AD that Riven has.
R - 
Blade of the Exile is Riven's ultimate. Activating it grants a flat 20% bonus AD, as well as increasing the range on her damaging abilties (
Broken Wings Ki Burst) as well as her auto attacks. It also allows the use of
Wind Slash
once, a powerful ranged attack that deals more damage depending on the enemy's remaining health. With a finished build (This one specifically) Wind Slash WILL kill any enemy with 1k or less health.
Riven's kit brings along combos with it. Knowing how to use her abilities to proc her passive and dominate trades is crucial to winning. Remember to ALWAYS auto attack in between abilities when engaged in a trade. If you only intend on harrassing, Broken Wings in, Ki Burst and then use Valor to escape. Be careful should your opponent have a stun or a slow, as this can mean you take more damage than you should when attempting to escape.
Laning at Top - Your opponent
I'll explain a little bit about taking 
Riven to top - by this I mean who to try and avoid going against, and a few champions who Riven will decimate.
AVOID (Unless you are extremely confident in your Riven skill)
Renekton - Very very much like Riven. He has her mobility, her damage, and, should he have fury, a much longer stun. This by no means you can't win out against him with the right playstyle. Take Valor first, and bring 
Cloth Armor and five 
Health Potion to negate his early game damage a little, and have some sustain.
Any top champion that has some ranged abilities. This goes for champions like 
Jayce, 
Rumble or 
Gangplank. Play safely, start with 
Boots of Speed and three Health Potion. Grab Valor first and then level your abilties as normal. When they attempt to harass you, Valor to negate most/all of the damage. Once again, having a champion like this doesn't mean you can't win. There is NO HARD COUNTER to Riven. Only soft counters.
You will win Versus:
Singed - Singed is a fairly easy lane once you know what you are dealing with. When going in for trades with him, try your best to use Valor to soak up damage from his poison cloud, or stay out of it completely. Once you have this down, Riven will always win trades with him, most of the time allowing you to bully him completely out of lane.
Irelia - She is extremely farm dependant at all points in the game, otherwise she becomes quite worthless. Use this to your advantage, Riven out-trades Irelia. Bully her out of lane, and deny her the much needed farm. She can become more of a problem if you allow her to progress in her build, but it still stands that, so long as you are equally as far in yours - you can beat her out.
Nasus - This dog is very much like Irelia. He is farm dependant, and, the more minions he kills with a certain ability, the stronger it gets. Deny him that strength, bullt him or kill him out of lane. Freeze the lane at your tower and zone him out. Nasus can get very tanky, so getting extra damage on him, or getting some early armor penetration will go a long way.
There's more champions in both categories, however, as you get better with practicing Riven (She has a high skill cap) you'll learn to win out versus her counters. Remember that, Riven isnt truly countered by anyone (In my honest opinion). Do your best versus your counters, and dominate the others.
Masteries
I take 21/9/0 for Riven in both top lane, and jungle. Having your masteries set up like this compliments your rune page, and once again, your early game damage and armour. This is crucial, and helps you be fairly tanky early game (This helps greatly against Rivens soft counters, the other top lane champions that are very much like her. Renekton for example, he can dish out a load of damage, and keep up with Riven's mobility). It also brings, once again, the damage you need in order to win trade offs at top lane.
Items
Starting off with Boots of Speed and three Health Potion gives you the speed that you need to help you get in, deal your damage, and get out quickly, aswell as bringing a bit of sustain. Immediately building towards 
Wriggle's Lantern and 
Ninja Tabi gives you some early game armour and damage, along with wards too keep you safe from the enemy team's jungler. After this, rushing 
The Bloodthirster and getting it's stacks should immediately put you ahead in damage against your top lane.
Next I begin to build towards a 
Phage / 
Frozen Mallet for it's health and damage bonuses, alongside it's champion-slowing passive. The health boost at this point in the game will keep you alive in those team fights and trade offs that you may get in to, allowing you to do your thing (By this I mean murdering the enemy champions). It also helps being able to initiate/tank for your team.
Finally, you can finish off the build with several items, these would be as follows:
-Get The Bloodthirster, 
Guardian Angel, and then swap out Wriggle's Lantern for a 
Last Whisper or a 
The Black Cleaver
-Get an 
Atma's Impaler and then 
Warmog's Armor, bringing yourself up to 3.5k+ health, allowing you to tank quite a bit. Then, swap out Wriggle's Lantern for either The Bloodthirster, or, should you need it, a Guardian Angel, or 
Thornmail if their AD Carry is strong.
-You may also choose to keep Wriggle's Lantern for either of these choices, as the free wards are necessary to keep tabs on Baron Nashor, and keep your teams map awareness/control high.
Remember, the final items are completely situational. If your team absolutely cannot afford you dying, always grab a Guardian Angel to stay in the fight. If you don't need the damage, don't be afraid to swap some out for more armour, or vice versa.
Unique Skills
General notes for Riven in no particular order:
Always remember as a general rule of thumb for playing Riven, do not, ever, spam your abilities. This would completely ignore the bonus damage that her passive, Runic Blade, grants. When you use an ability as Riven, you gain one stack of her passive, which grants bonus damage on your next AA, stacking up to a cap of three. Spamming her abilities would instantly cap you on her passive, meaning you are missing out on the extra stacks that you would gain with auto attacking in between abilities.
Also, about mid game, you should be progressing in your build OK. Remember to initiate for your team. Stay in the front, initiate, popping Blade of the Exile, and then jumping in with your combos. Finish off strays with Wind Slash to ensure no one gets away.
Remember that Riven's E Valor scales off Attack Damage. Late game, activating Blade of the Exile and using Valor to step in and initiate, you get an amazingly large shield. It can definetely be the difference between life and death.
A general tip for going against one of Riven's soft counters, like Renekton for example, is to play safe. DO NOT attempt to win a trade with Renekton should he have fury. To win a trade with him, wait until he blows off all his fury with one of his abilities on minions, and then quickly jump in, Ki Shout and then Valor out. If you are against a champion with some kind of ranged poke, like Jayce or Rumble, save Valor until they make an attempt at poking you, get your timing right, and your shield can block most, if not all, of the damage they would've dealt.
Team Work
This build can be very team dependant early on, requiring the rest of the team to be able to stay in the game, and avoid being shut down in their lanes. As long as this happens, it prevents champions other than the jungler and the enemy solo top from coming up and delaying your farm. Late game, once the build is nearing completion, stay at the front of the team when there is about to be an ingagement.
Your tankiness and high mobility allow you to easily initiate fights, using her ultimate, alongside her ability+AA combos to dish out damage and control the fight. Finish any stragglers off with a second R (Wind Slash) at a range, dealing more damage the lower the health your target(s) have. Remeber that Wind Slash can hit as many enemies as you want, as long as they are in range of the cone and your aim is proper.
Pros / Cons
Pros:
-Extremely strong late game - you don't fall off and become useless, as many champions can late game
-Very complimentary to almost any team comp
-High survivability - you shouldn't and won't get killed often
Cons:
-Only decent early game - you are somewhat weaker than a glass cannon build
-Very reliant on your team - if they get shut down and the game ends early, it denies you your full late game potential
Summary
That is about it folks. This is my Riven guide, as I've gotten bored of the low amount of variety I see with Riven builds today, ingame. I prefer the tank-damage mix this build and my variants give, along with the high survivability late game.
I hope you enjoyed this guide, and that it helps Riven players new and old with playing her, as she is by far my favourite champion. It would be great to see this used more often (From my perspective, this build is more complimentary to her than going glass cannon, as she is a bruiser, and this works around that.
So have fun, dominate some games, leave a rating, and, if you come up with some item or mastery replacements that may benefit her more, be sure to let me know with a comment, I'm very open to suggestions (Should they be polite ones, that is, not trolling or raging at me)
Thanks!
-Note, if you have the time, please support my friend's Volibear guide here : http://www.mobafire.com/league-of-legends/build/thunderous-jungle-a-guide-to-volibear-in-the-jungle-231861
Some screenshots of recent Riven games
More to come when imgur stops failing
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Build Guide
Discussion (6)
Greater Mark of Attack Damage, nine 
Greater Seal of Armor, nine 
Greater Glyph of Magic Resist, and three Greater Quintessence of Strenth. This is because of Riven's insanse abilities as a bruiser.
Flash on 
Exhaust, to help chase, and ensure that I will win fights with my enemy, lowering their physical damage and move speed. If I'm in jungle, I replace 
Smite, and keep 
