From the November 2011 issue of PC Gamer comes pictures of...
Riven: "The Shattered Exile"
"It's never too late for redemption. This former Noxian soldier has forsaken her malevolent compatriots on a quest for self-discovery, wielding a shattered sword to remind her of the fractured world she left behind. Her high-mobility playstyle is reminiscent of arcade fighters, with the ability to combo skills in quick succession for maximum damage. When she gets her ultimate, people will die: her sword reforms to unlock its full power, sending massive energy waves crackling through the air with each slice."
Plus her pretty hot sword:
Magus: "The Magus Ascendant"
"This caster champ, a being of pure energy, perfectly captures the feeling of uncontrollable power. He charges up energy with each spellcast, temporarily increasing the damage and cost of subsequent spells. Playing him will be a tricky balancing act between knowing when to open the floodgates and pour out your damage, and when you're better off taking the slow-and-steady route"
The main image of Magus as a white ghost with armor and chains is his "super-charged" form, while the bottom shield-like image is his "low-energy" form.