This is an Offtank Riven build. Preferably solo top (Only if they have a jungler. I've tried and had almost very little success 1v2 as Riven. She can't farm :c)

I love playing Riven. Her skills require a little bit of timing and strategy to get down, which I find plenty of fun in, as well as being amazing in lane and in the middle of team fights. This makes Riven my absolutely most favorite melee AD champion. The fact that she is almost impossible to turret dive, her skills work well in team fights, and her ultimate gives her AD a % boost is just amazing and will make your head spin when you find out all of the amazing things that you can do as a Riven.

In Noxus, any citizen may rise to power regardless of race, gender, or social standing – strength is all that matters. It was with committed faith in this ideal that Riven strove to greatness. She showed early potential as a soldier, forcing herself to master the weight of a long sword when she was barely its height. She was ruthless and efficient as a warrior, but her true strength lay in her conviction. She entered battles without any trace of doubt in her mind: no ethical pause, no fear of death. Riven became a leader amongst her peers, poster foal of the Noxian spirit. So exceptional was her passion that the High Command recognized her with a black stone rune sword forged and enchanted with Noxian sorcery. The weapon was heavier than a kite shield and nearly as broad – perfectly suited to her tastes. Soon after, she was deployed to Ionia as part of the Noxian invasion.

What began as war quickly became extermination. Noxian soldiers followed the terrifying Zaunite war machines across fields of death. It wasn’t the glorious combat for which Riven trained. She carried out the orders of her superiors, terminating the remnants of a beaten and fractured enemy with extreme prejudice. As the invasion continued, it became clear that the Ionian society would not be reformed, merely eliminated. During one bitter engagement, Riven’s unit became surrounded by Ionian forces. They called for support as the enemy closed in around them. What they received instead was a barrage of biochemical terror launched by Singed. Riven watched as around her Ionian and Noxian alike fell victim to an unspeakably gruesome fate. She managed to escape the bombardment, though she could not erase the memory. Counted dead by Noxus, she saw an opportunity to start anew. She shattered her sword – severing ties with the past – and wandered in self-imposed exile. Now she seeks atonement and her own way to serve the pure Noxian vision in which she believed.

“There is a place between war and murder / in which our demons lurk.”
- Excerpted from the poem, “Scarlet Shon-Xan”

Pros
Amazing Offtank
Sexy
Not that item dependent
Ult is similar to Garen's
Amazing AD Ratios
2 disrupts
Shield/Dash
Spammable AoE Stun

Cons
Is somewhat difficult to play
Requires some kind of strategy to play as
Passive needs some brains to use
Susceptible to Crowd Control

The rune explanation should be a little simple.
This rune setup is geared toward early lane phase dominance as an Offtank Riven.
This rune page set up is very common for other offtanks.

Greater Mark of Desolation
Since your Broken Wings, Ki Burst, and Blade of the Exile do AD Damage, you don't want any of early game armor to impede on your early game harass

Greater Seal of Armor
Since you're going to be solo top, or duo lane, chances are that you're up against an AD champion. Since Riven's base armor is pretty low (Like almost every other champion out there) you want to get some early game armor that can also carry into mid and late game.

Greater Glyph of Magic Resist
Just to be a little tankier against those annoying AP harassers, this is for you. However, this doesn't make you invincible. So make sure that you try to avoid their possible harass as much as possible.

Greater Quintessence of Health
78 extra HP at level 1? Nuff Said~

Time to explain some items--

If you're solo top, grab a Doran's Shield. If you don't feel like that, then get yourself a Doran's Blade. I prefer to start out with these two items, because it gives a lot of good base stats that can help you out lane phase.

Doran's Shield makes you tankier than you already are (I always enjoy that feeling when I can harass my lane freely and take almost no damage from their Ranged AD :3) Even if you do take a lot of harassing, you get an extra 8HP / 5 seconds added to your masteries.

Doran's Blade gives you a little more AD, as well as some lifesteal (works with your passive) and some extra HP.

With your choice of boots, (preferably Mercury's Treads since CC shuts down Riven and her combos) comes your Wriggle's Lantern and The Brutalizer

Even after the recent nerf, Wriggle's Lantern is still an amazing item, at a cheap little package. Upgraded madred's passive for a little punch with your in-lane farming, some lifesteal that helps out A LOT, armor, and extra AD. As well as a free ward every 3 minutes (which is when the ward also runs out) is also very nice. (As well as Wriggle being one of my favorite background characters. Oh how Wriggle x Yuka is my favorite shipping :3)

After a little farming, you should be able to get your Brutalizer next. This item is nice since it gives Riven some Armor pen, CDR, and extra attack damage, all for a simply cheap 1337 gold (If you don't get the joke, then you haven't been on the internet long enough :D)

Once you get your Brutalizer, you need to save up for your really big buy. Once you get your next item in your build, you're set. What I'm talking about of course, is the infamous Warmog's Armor At an awesome 920 extra HP, and 30 HP/5, this item is amazing. As well as having an awesome passive, Warmogs is the perfect buy for any off-tank AD build. The passive helps you out if you buy this early, so by the time you should have gotten your warmogs, it should only be around mid-game, which is around 20-30 minutes in.

And no Offtank Warmogs build is complete with--you guessed it-- Atma's Impaler
With the Atma's effect, you're going to have an awesome extra 50-60 AD, as well as getting 70 armor AND 18% crit chance. This item is a great steal, and can be interchanged with the Warmog's in the build. Which item you decide to buy first is your preference. But I feel that Riven doesn't have a lot of base HP to benefit from the Atma's Passive as much as she could, so Warmog's is always my first buy.

Okay, so two Touhou items in one build? What!?
Yeah, that's right. The only other Touhou referenced item in the game is the Youmuu's Ghostblade
You're going to upgrade from your puny little Brutalizer, into the big boys.
But don't forget-- Take advantage of the item's active effect :D

Now once you're at the late game stage, and you have enough gold to drop your Doran's Shield for something a little bit fancier, get a little more Magic Resist. Masteries and runes are fine and all, but items always help. I get a Force of Nature for the Hp/5 and Awesome Magic Resist. Other good Magic resist item is Banshee's Veil since it can actually block a spell, as well as giving you extra HP. Too bad the MP goes away, but this is late game, as well as your last item. Who cares about wasting gold? XD

If you feel like your Wriggle's Lantern is slowing you down a little, feel free to trade it in for a Zeke's Harbinger. The extra Lifesteal and armor reduction is always nice.

Why Exhaust + Flash ?
Because they're amazing summoner spells. Exhaust helps you chase, run away, and fight. Flash helps you get over walls to help you escape, or go in to help initiate the team fight with your team. (It's not recommended to do this. The normal tank should do this. However, if you don't have a main tank, then as the Offtank, it is your job to go in the middle and initiate.)

Decent Spells:
Ghost Gives you that extra movement speed to run away, chase, or initiate the team fight.
Teleport Helps your turrets/team mates in a pinch. Especially since you can teleport to wards again.
Ignite grievous wound as well as true damage. This can help get the kill that runs away if they get too far, or can also help you fight that AD that heavily relies on his lifesteal.

All of the other spells lack in synergy with Riven, and I choose to not take them.

Early game:

You want to make sure that you get a lot of last hits. Whether you're in duo lane or solo lane, get as many last hits as you can. Last hits are essential in your life. If you want to harass, you want to walk up in between your opponent's melee minions and the caster minions. Shield Dash towards your enemy, hit your Q, Auto attack, Q, auto attack, stun, Q, and run away. Remember that the final hit on your Broken Wings knocks enemies back, so take advantage of that brief delay to get away from their attack range. Also remember that your passive has a stack cap of three, so if you're mindlessly spamming your skills around like there's no tomorrow, then your passive's potential and damage output will go to waste and wither away.

Another important tip: MAKE SURE that after your combo, you run away. Early game Riven has very little damage output without her passive and skills.

Also, when you get your ult, don't use it until you're guaranteed a kill. Ult first, combo, auto attack, and then activate ult again to get that runaway kill.
Sometimes your ult can also be used as a bluff, making your opponent waste one of their summoner spells. Remember that your ult is only on a 60-70 second cooldown. Their flash/ghost is on a 250 second cooldown.

Mid Game

Roam. Roam. Roam.
As Riven, you want to gank as much as humanly possible without pissing off your lane partner too much. Since Riven has two chasing tools, and a stun, she is a great ganker, as well as a fast traveler. Take advantage of her dashing skills and use them in between ganks to help speed you up.
By this time, you should have enough farm and kills/assists to have your Boots, Wriggles, and Brut. Maybe even a Giant's belt if the game is going well for you. Remember that your combo still holds true, even late game. You are at your weakest when your cooldowns are up. Make sure that after they are debilitated, that you try and get away to farm your lane again.

Team Fights/End Game

Team fights! Team fights! Team fights!
Your job as the offtank is to go in right behind the tank, take some of the damage, and kill their squishy. If you don't die, well then, that's a plus for you. But you want to get as much aggro off of your squishy ashe as much as possible by doing as much damage as you can while being as tanky as you can.

When using your ult, it's always nice to try and get as many enemies as you can inside the cone of instant death. Since minions are always a good money source. Always. :3

Also remember, that by this time, you should probably have a Youmuu's Ghostbladeso take advantage of its active by spamming it in teamfights, greatly increasing your DPS.

With this guide, I hope that you can have as much success with Riven as I've been having. She is always a fun choice as an offtank in any kind of play.

If you have any kind of suggestion, put it as a comment and I'll be sure to mention your screen name in this guide :)

What I wouldn't recommend is playing Riven in solo queue. Her skills and lack of early game damage is made up with great teamwork, just like almost every other offtank out there. So remember kids: Play safe, and make some friends! Have fun! :D

~RoastKilla778