Combine the compatibility of the game pass core with the features of ultimate game pass.

Hi Jacob. My name is Kyle and I'm an independent advisor.

Thank you for posting on the Xbox Communities Forum. Sea of Thieves is not included in Game Pass Core's library of games. Game Pass Core or Ultimate is required to access the game's online features, but if you haven't bought the game and were playing it through Game Pass Ultimate, you'll need to keep your Ultimate subscription to continue playing.

Or you will need to purchase the game separately if you'd like to keep your Core subscription.

the upgrade from Xbox Game Pass to Game Pass Ultimate combines Game Pass with Xbox Live Gold, that is why Game Pass Ultimate costs more than standard Game Pass, and the combined cost is cheaper than having Live Gold and Game Pass as separate subscriptions

There are 4 versions of Game Pass.

Game Pass Core, Game Pass for console, Game Pass for PC, and Game Pass Ultimate.

Only Game Pass Core and Game Pass Ultimate include the ability to play online multiplayer games.

Is your subscription for one of those two or is it just Game Pass for console?

I understand, as this is an Xbox 360 game that is used via backward compatibility, it requires an active Game Pass standard, Game Pass Core, or Game Pass Ultimate subscription.

Additionally, you must sign in with your Xbox profile and this will allow you to play this game online

Yes, Game Pass Ultimate includes online multiplayer.

Core is essentially the new name for Gold. Gold is becoming Core which will also include a small amount of game pass games. Game Pass Ultimate will remain the same as far as including Core (online multiplayer), Game Pass for console, PC Game Pass ,etc.