Currently during the whole mage revolution, only 4 champions (Lux, Sylas, Garen, and Jarven) have appeared with two others being hinted at. (Kayle and Morgana)
I know it's suppose to be the story of Lux and Sylas, but it's weird how every other Demacian champion is missing and unaccounted for. You'd expect champions like Xin Zhao (The Lightshield's Steward), Vayne (Who hates black magic, or magic in general), Shvyana (Who is an Elite Guard) or Galio (Who gets awaken by magic) to make some type of appearance or mention.
While some can be explained like Fiora caring too much about her house's reputation to bother helping out. Vayne was last spoted in the Freljord and was injured.