Sure, developers issue assets on Stellar for each collectible class they want to provide in their game. On the platform, Stellar accounts (public key or federated names) are used with token based-auth to ID and verify gamers so the game server can directly check that the player accounts are holding the asset and their balance (if needed), then perform any update necessary on the game data for that play session.
Additionally, developers can list the collectible items in the game shop accessible from Litemint. If the player does not have a trustline, he is given the opportunity to add it. When there is an active market on the Stellar DEX, the best price is listed. This price is resolved through path payment search from the selected wallet currency. The resolution through path payments allow buyers to use any currency for which a route can be found, this also allows sellers to choose a different quote currency than XLM which may not always be practical to use as overflow can happen (to prevent subdivision, item may be counted in stroop and high listing prices would overflow in XLM).
That’s for collectibles, developers have also access to standard cross-currency in-app payments implemented on Stellar DEX as well to sell in-game items without the need to issue assets which can help provide a smoother experience to players. For these items only the payments are decentralized, DEX trading is not possible. I am working on a game that would combine both ways allowing players with the trustline to trade but players without to still enjoy the item in game without the ability to “export/trade” it.