Decided to write this as an article to expand on a comment I wrote somewhere else.
There has been quite a lot of buzz over blockchain games where there is the premise that the items within the game can never be nerfed or buffed due to the the items being stored on the blockchain. However this may not be entirely correct.
What usually happens in blockchain games is that the game publisher issues you a non-fungible token that represents the item within the game. For example, when you purchase an item, they provide you a token with the unique ID “123456789”. This unique ID represents an item within the game, where the game assigns attributes to the item. In this case, it will still be possible for items to be nerfed since the attributes are assigned by the game and not the token. For example, this item ID "123456789" used to be able to do 100 damage in-game. However, the game publishers decided to do some balancing to the game and decided to assign 10 damage to the item instead. This changes nothing on the blockchain as the item ID still exists in the player's wallet, but the representation of that item within the game changes.
If you need further proof, you can check the GodsUnchained FAQ where they have a disclaimer on cards being nerfed or buffed during the beta phase, even though they are using the Ethereum blockchain to store the items. Like I said, the ID and ownership of the asset does not change, but the representation of the item within the game can change.