LoL's Newest Champ, Lucian the Purifier, is not available for purchase.
Lucian, whose wife was killed by reaper champion Thresh, is Riot's newest champ. He is a righteous man who fights across League of Legends' Shadow Isles in his wife's honor. (His wife Senna is expected to be a champ introduced later in the game.) The champ is available now for 7800 IP or 975 RP. However, Lucian and his badass Hired Gun Lucian skin are also on sale in a bundle for 1462 RP, down from 1850 RP normally.
We have broken down Lucian's abilities here, and make sure to check out the below video with Lucian's Champion Spotlight.