It's a very thorough interview process. A call with a recruiter, job fit call with the HM, and a half-day of onsite behavioral interviews with a number of people. LOTS of behavioral questions ("tell me about a time..."). Be familiar with the STAR method of answering and PROVIDE EXAMPLES of the behavior. Onsite also included a work sample.
One culture-type interview felt more like another reviewer said, very "why do you deserve to be here?" rather than trying to understand and dig into the answers I was providing. Felt like the interviewer wanted a specific answer to a subjective question with no real "right" answer. It was the only interview I came out of confused about my status in the process. The HM was clearly looking for a VERY specific type of person for the role.
I was ultimately turned down because of lack of LoL experience, something I was more than willing to jump into for the role. I was independently told that this is not "supposed" to be a marker for hiring anymore at Riot, so be aware.
Overall, felt the process was challenging without being overly difficult and really enjoyed most of my conversations with the interviewers.