Lane pressure with maximum Summoner Cooldown use.
Creative tools and rule bending
Your first 2 attacks after using an ability on champions grants gold and sometimes consumables.
Gain a free stopwatch. Stopwatch has a one time use Stasis active.
You can enter debt to buy items.
+5% Max CDR
+5% Summoner Spell CDR
+5% Item CDR
Empowered abilities and resource manipulation
Gain 10% CDR when you reach level 10. Excess CDR becomes AP or AD, Adaptive.
Gain increasing amounts of AD or AP, Adaptive over the course of the game.
+5 AD or 9 AP
+6 Armor or 8 MR (match-up)
Klepto on Riven synergizes well with your ability spam combos, allowing you to generate a lot of extra gold during the early laning phase.
The stasis active allows you to make out-plays and survive a close tower dive to snowball your lead. It also grants you a cheaper Guardian Angel.
Future's market lets you hit you item power-spikes extra early. When combined with Lethality, your mid-game damage will be incredibly high.
Riven's mana-less kit means that CDR is one of her absolute most important stats. The extra bit of Summoner CDR also means more Flash and Ignite pressure.
As a mana-less champion, Riven heavily relies on ability spam to deal damage. More CDR means more casts and more opportunities to kill.
The bonus AD granted from Gathering Storm makes you a late-game monster, able to one-shot any backline champions with the right opening.