Pros
I was working at Riot Games as an MBA intern this summer. It is a truly meaningful experience. Seldom could we work for a company at such rapid growing stage, yet there are already lots of amazingly smart, humble, and passionate people who you could work with and learn from every day! There is no routine or fixed type here. Everyone and everything is unique. You can define your experience and others' experience here.
Cons
Having said that, you might have realized that it's challenging to work in such an environment if you are not a person who likes high autonomy, solving ambiguous problems without much guidance, and can work in a messy situation. If you are looking for well-structured training and guidance, Riot might not be the place for you. Here, you have the freedom to create and grow, but you have to be able to take care of yourself and have a good judgement on when to DIY and when to seek help. And if you don't like fast-paced, sometimes high pressure, and always changing work, then prob. you'll feel very stressed here. It's good to step out of your comfort zone, but you cannot go too far if the challenge gives you more harm than good.