Riot just announced that all League champions and Valorant agents are coming to Game Pass

pcgamer.com:

During the Xbox and Bethesda not-E3 showcase, Riot Games showed up to announce that its gaming roster will be available on the Xbox Game Pass. Riot's games are already free-to-play, but the draw here is that champions, agents, and cards will be instantly unlocked for Game Pass subscribers. And that's sort of sick (for Game Pass subscribers). 

Riot Games' monetisation model relies on people wanting to buy in-game items. Though many of these items would be cosmetics like skins, the system also allows players to unlock Champions in League of Legends or Agents in Valorant by spending money. You can earn them instead, but the time to unlock these characters through playing can be a drag. This is most evident in League of Legends, where there are over a hundred options available, so making them all free on Game Pass is sort of massive. 

Here's the full breakdown of what you'll get on Game Pass: All champions in League of Legends, League of Legends Wild Rift, and Agents in Valorant. Additionally, the Foundations Set is unlocked in Legends of Runeterra, and select Little Legends are unlocked for Teamfight Tactics. This deal will apply to both PC and mobile versions of the games. 

There Riot stuff isn't on Game Pass just yet: The trailer says it's «coming this winter,» which could mean the end of 2022 or early 2023. Additionally, the video's end card mentions that XP boosts «and more» will be included with Game Pass. I'd guess the «and more» could be like Amazon Prime's additional skins or in-game loot which are just available to Game Pass subscribers, but that's just speculation.