The cover art for the upcoming second issue of The Rise of Kylo Ren, a four-issue comic mini-series the focuses on the origins of Kylo Ren and the Knights of Ren, has revealed that a young Ben Solo and Luke Skywalker once fought together against the Knights of Ren.
Revealed by The Rise of Kylo Ren writer Charles Soule, the image by Will Sliney shows Solo, who will eventually become Kylo Ren, and Skywalker facing off in the rain against at least 5 Knights of Ren carrying various weaponry.
Source: IGN.com Luke Skywalker and Ben Solo Fight the Knights of Ren in New Star Wars Comic