Free for everyone
Riven vs Aatrox
Stay out of his Q sweet spots and punish the gaps between them.
Aatrox wins long fights. Your job is to keep every fight short.
Stand outside the edge of his first two Q casts, then trade while the third is on cooldown. Hit him with Q and W, and back off before his healing turns it around.
Once he has his ultimate, give him room until it ends, then go again.