ERC-998 and the Future of Blockchain Game Assets

Brian Burns
Published in
5 min readSep 5, 2018


CryptoRome, built by the GigLabs team, is the first game to build and release ERC-998 composable tokens to its players. This breakthrough allows players to not just purchase villages but to grow empires — all through a single token of ownership. From the player’s perspective, management of the asset becomes simpler, costs go down and value of the asset multiplies. The ERC-998 standard is the foundation of our game and we believe will be the foundation for more games going forward.

If you play blockchain-based games, the following may make you shudder:

You’ve spent countless hours building your in-game character. You’ve leveled him up and equipped him with all the goods — helmet, sword, armor, etc. However, the time comes and you want to trade or sell off your character along with all of the character’s belongings. Each item is an ERC-721 non-fungible token (NFT). This means you must individually transfer or sell them off one-by-one. The horror! This is not only unmanageable, especially given the number of assets you own across multiple games, but it is also cost-prohibitive from a gas perspective.

This is obviously not an ideal customer experience and is a big deterrent for blockchain game adoption in general. This scenario also presents a huge barrier for game developers who would like to scale gameplay using more NFT integration.

The ERC-998 Composable NFT standard presents a better way and we’re proud to be the first game to use this.

What is ERC-998?

Ever since CryptoKitties, ERC-721 has quickly become the de facto Ethereum standard for creating unique, digital assets known as non-fungible tokens (NFTs). ERC-721 tokens can represent anything from kittens to collectible baseball players. I wrote about this standard and its real-world applications in an earlier post.

ERC-998 acts as an extension of ERC-721, allowing you to “compose” a new token from a group of ERC-721 assets. Your in-game character can now be composed of all of its underlying NFTs: shield, sword, boots, special items, and even other ERC-20 tokens. When you are ready to sell or trade the character, it takes just one blockchain transaction, after which all underlying assets belong to the new owner.

Sudden value creation is a big deal

A composable asset is a powerful concept. ERC-721 tokens are already unique and (generally) one-of-a-kind. The ability to compose ERC-721 assets into brand new creations suddenly gives users limitless opportunities for new value creation.

The most basic examples of ERC-998 I have seen involve dressing up your digital avatar or adding glasses, hats, and digital art to your virtual cat. The example below shows an example of attaching ERC-998 tokens to an existing ERC-721 CryptoKitty, resulting in an entirely new creation.

ERC-998 Bottom-up Composable — Original graphic created by Abhishek Chadha

While this is a fine use-case, there are more far-reaching implications for how this standard can be applied. The next use-case we’ll look at is how our team at Giglabs is utilizing this standard for assets in our game, CryptoRome.

Using Composables for (Virtual) Land

CryptoRome is the first game to build and release ERC-998 assets to its players. Land ownership is key to advancing in CryptoRome. Land, the ERC-998 token in this case, allows players to produce resources and build improvements so that they can gain stronger armies and conquer more lands in Europe.

When players start acquiring large numbers of lands, managing, transferring, and improving lands gets to be an unwieldy proposition. Thus there needed to be a way for players to compose lands into larger settlements (and also decompose them back to their smaller parts as desired).

Land composition of a City in CrytpoRome (13 tokens altogether)

The above graphic shows the full makeup of a city in CryptoRome, complete with its component towns and villages. In essence, it’s a tree of ownership. A player, by virtue of owning a city, would indirectly own all underlying component lands. In addition, the player would only need one blockchain transaction to sell or transfer the entire city structure to another player. Using the city example above, that’s effectively 13 NFTs changing hands in one shot!

Exploring other use cases

In the context of the CryptoRome land tokens, ERC-998 has opened up the possibility to compose land onto new or existing ERC-721 tokens in the future, some which could be created by other developers. The below diagram shows one example of what is possible.

Example: Composing lands into a future token asset

One obvious possibility is that someone could create a higher-level ERC-721 token contract to hold groups of lands. It could be a province, a nation-state, or even an economic alliance with other players.

Note that the higher-level ERC-721 does not need to be ERC-998 compliant and does not even need to be created by the CryptoRome dev team, as the existing ERC-998 land tokens can compose onto the ERC-721 in bottom-up fashion (more on this in a future post).

Let’s revisit the use-case brought up at the beginning of this post. You create a virtual character (or virtual avatar). Your character may own a number of other assets, some of which may also be composable assets (such as a CryptoRome city composed of villages), or even ERC-20 tokens.

Ownership example using a virtual character or avatar (character could be ERC-721 or ERC-998)

What an interesting concept! You still indirectly maintain ownership of all of the character’s items by virtue of owning the avatar. However, you could easily choose to sell your character, along with its entire composition of assets, with one listing and one transaction (likely at a higher value than the sum of the individual parts).

Adoption On the Horizon

We are excited about this standard and where it can take us. ERC-998 opens up a number of possibilities, and that will only grow as other games adopt the standard.

Moving forward, network effects will play a large part in the growth of composable NFTs. The more companies and games that build ERC-998 NFTs, the more you’ll see other games incorporating cross-game assets. It is a win-win for the blockchain gaming industry.

I will continue with a series of posts on ERC-998, and delve into some of the more technical aspects, so please stay tuned!

Our links:

CryptoRome Website:
GigLabs Website: