Riven featured in PC Gamer soon after she was announced (her title was changed to 'the Shattered Exile' when her 'Champion Sneak Peek' was released, later reverted to the current one when her 'A New Champion Approaches' preview was released)
She celebrates the Season 2 World Championship (she started out as a regular skin that had to be redesigned for the Finals) and references the Roman II (featured on her chest, back, while Valor is active, and her sword being broken in two pieces)
She became Legacy since then (was unlocked for a perfect score in Worlds Pick'em 2015) but returned for the Season 6 World Championship in two versions: 'Championship' for those who unlocked her in Season 2 (featuring a crown on her head and added extra particle effects on her sword) and 'Championship 2016' for those who unlocked her in Season 6 (basically her first incarnation)
Mythological inspirations are possibly the Indo-European Dawn Maiden Hausos & the Semitic angels.
Riven was a Noxian soldier sent to Ionia during the empire's invasion. A traumatic experience during the campaign involving Singed's chemicals caused her to question her devotion and sever her ties to Noxus, wandering ever since.
Yasuo suspects Riven of being the one who killed the Elder he was supposed to protect ("Wait, that technique... huh", "Huh, three swift strikes... ", "Another wind blade?", "Who taught you that?")
↑G. Kroonen, Etymological Dictionary of Proto-Germanic, p. 412