Blizzard and Xbox have announced that if you buy Obsidian's upcoming action RPG Avowed on the Battle.net platform, you'll be able to play it on Xbox, and the reverse is also true.
In a post on the Blizzard website, the company grandly proclaims that the feature "breaks down barriers with cross-buy" and confirms that Avowed represents the introduction of this feature between Battle.net and Xbox, suggesting more games could support it in future.
In short, if you buy Avowed on Battle.net, then by linking your Xbox account with your Battle.net account, you'll be able to pick up where you left off on Xbox and won't need to buy the game again on that storefront.

If you're wondering why this is a thing, we've racked our brains here at TechRaptor Towers, and the only real benefit we can come up with is that this will technically allow you to play Avowed on both Xbox and Steam Deck.
The Steam Deck doesn't play very nice with the Microsoft Store, but with a little fiddling under the hood, you can install Battle.net on your Deck and it'll work alright. As such, it should theoretically be possible to play Avowed across Xbox (or PC) and Steam Deck.
Of course, if you're going to play the game on PC exclusively (for which you'll probably want a pretty good machine), then there's really no reason not to just pick it up on Steam, and I can't imagine any other use case where someone might find it useful to switch between Battle.net and Xbox.
Avowed is the latest game from Pillars of Eternity and The Outer Worlds developer Obsidian. Appropriately enough, it looks rather like a combination of those two games, marrying the first-person action of the latter with the setting of the former.
Initially, it was announced that the game would run at 30fps on Xbox Series X|S, but Obsidian has since confirmed that it will implement a 60fps mode for the game on consoles.
You'll be able to check out Avowed when it launches on PC and Xbox Series X|S on February 18th. It'll also be available on Game Pass on day one, assuming you're signed up to the PC or Ultimate tiers.