I applied through a recruiter. The process took 3 months. I interviewed at Riot Games (Santa Monica, CA) in June 2017
Interview
Phone screen -> Team call -> Art test -> In person day interview (6 hours)
Very friendly people, unfortunately no offer. The second call is usually the most challenging prior to the in-person interview. Be certain you know a lot about League and Riots culture.
1 on 1 with about 5-6 people in one day. It took 11am - 5 pm and took 30mins to 1 hour per interviewer. someone was more casual and someone was more serious