Ginno Games, the developer of Devilian, announced the closure of the South Korea server and getting the rights back from publisher Hangame (NHN subsidiary). Player data will be kept intact until a new publisher is found. It was revealed a few months ago that NHN is seeking to move away from PC games to focus on mobile games, including TOAST. Trion Worlds announced Devilian recently.
Note: Devilian is still getting new content, as the 5th playable class was teased for the China server and more confirmed in development. The game should get a new publisher in South Korea soon.