Mythical Beings cards on the Polygon Network!

Mythical Beings
7 min readNov 12, 2021


The Mythical Beings NFT card collection will soon have a bridge to OpenSea on Polygon, one of Ethereum’s Layer 2 blockchains. In this blog post we explain what that means, how it will affect users and the dynamics of the collection, but first, we take a look at the new smart-contract that makes this all possible.

1. Overview.

An NFT is a “digital object” that inhabits a decentralised ledger, a blockchain. Its use has all the advantages that this digital technology provides, in particular its ease of transmission, its full possession by the owner of the private keys, and the possibility of being created under a transparent and verifiable code. However, there is a cumbersome limit to this technology, and that is that blockchains do not communicate easily with each other. Because of this, an NFT created on a particular blockchain cannot, normally, be used on platforms that are based on a different blockchain, and this fragments the NFT space and leads to the loss of useful synergies for all actors, including collectors.

In particular, the Mythical Beings collection, which inhabits the Ignis blockchain, was unable to access some large NFT marketplaces, which are built on blockchains using the Ethereum Virtual Machine.

For the same reason, the set’s usage statistics have been ignored by the main ranking pages, despite a volume of sales and trades that would make it one of the most active sets in the NFT space.

Over the last few months Tarasca has been studying the possibilities to solve this problem, converting Mythical Beings cards into multi-chain objects, which can travel from one blockchain to another without losing their scarcity attributes. Finally, we found a Bridge model that, supported by Ignis smart-contracts, allows users to block cards on this chain and, in doing so, unblock the equivalent cards in Polygon, Ethereum’s L2. In the design of the Bridge we had help from the community dev Tre, and the smart-contract was developed entirely by Jelurida devs. To all of them, thank you very much!

This smart-contract, on the other hand, is not specific to Mythical Beings cards, but can be freely used by any Ardor project, to convert any asset or NFT into multichain. It is hard to overstate the importance of this smart-contract, as it turns the entire platform into a cross-chain technology, and opens the door for any NFT or digital asset, native to Ardor or any other blockchain, to use Ardor’s incredibly robust features.

2. The smart-contract.

The smart-contract will be open sourced by Jelurida and made available to the community at a later point in time. Here is a simple summary of how it works. If you would like to know more, just get in touch through the usual channels of Tarasca or the Ardor community.

A. Card creation.

The first step is to create cards in Polygon. An account created as many cards on this chain as exist on Ignis: every creature has its NFT, with the same supply as on Ignis. The cards will be represented by ERC1155 tokens on Polygon.

B. Blocked accounts.

The bridge node operates two accounts, one on Ardor and one on Polygon, where the cards will be blocked. The Ardor Blocked Account (ABA) is a new account that starts with a zero balance. The Polygon Blocked Account (PBA) is the account that has created all the cards in that chain, and starts with a balance equal to the entire supply of the collection.

C. Linking accounts.

The smart-contract is developed in Java and running as Ignis lightweight contract, which will control both the ABA and the PBA, so that it will only unblock cards on one chain if the user has previously blocked cards on the other. The smart-contract resides on Ignis and directly controls the ABA and PBA.

In this way, the total number of cards in circulation will always remain stable, guaranteeing the stable supply: the contract ensures that the number of cards in circulation on Polygon will be identical to the number of cards blocked in the Ignis ABA.

D. Ignis to Polygon: address as attached message.

Whenever a user wants to send Ignis cards to Polygon, he actually transfers those cards to the ABA, where they are blocked, by adding a message with his Polygon address. This allows the smart-contract to build the transaction on Polygon, unlocking the cards from the PBA to the address provided by the user.

E. Polygon to Ignis: custom deposit address.

Since messaging is not consistently implemented in EVM based wallets and platforms, the decision was made to use individual Polygon deposit addresses for each user on Ignis. This address is generated by the Bridge for the user’s Ignis address. This way, every time the user sends cards to that address, he can ask the contract (“Start Swap” button) to execute the transfer. If the smart-contract verifies that the address has received cards, it will perform two operations: send those cards to the PBA, and release the equivalent cards in the ABA, sending them to the user’s Ignis address.

3. Operation and uses.

This design of the bridge, although the technology is somewhat complex, created the possibility to offer you, our user, a simple to use interface. We find the result remarkable: the whole process is triggered with a few clicks from within the Mythical Beings wallet, or directly from within OpenSea, and only takes a few blocks to confirm the transactions on both chains.

This is the step-by-step process from the user’s point of view:

  • A user has a account.
  • And also has an account on OpenSea, where he wants to trade his cards. These accounts are usually managed by Metamask or other Ethereum wallets.
  • The user accesses the “Bridge” section of the wallet, and chooses the option “Send to Polygon”. In this section, they select the card they wish to send and the amount, and paste their Polygon address in a box. Just click on the send button, and wait a few minutes for the contract to do its job. The cards will automatically appear in your OpenSea balance.

You can see the whole process in this video. It is testnet, but it shows how it works and takes less than 2 minutes.

If, on the other hand, a user has acquired the cards on OpenSea and wishes to send them to Ignis, for example to participate in the game, they will have to do the following:

  • Open an account on
  • Access the “Bridge” section of the wallet, and choose the option “Send to Ignis”. A personal Polygon address will appear, the deposit address, to which they need to transfer the cards.
  • In OpenSea: Send as many cards as you want to that personal deposit address. Once they are sent and confirmed, you click on the “Start Swap” button in Mythical Beings, and the smart-contract will take care of everything. Within minutes, your cards will be in your Ignis/Mythical Beings wallet.

Here you can see a short video with the process:

With this easy-to-use system, current Mythical Beings users will be able to trade their cards on OpenSea, a main NFT platform, using alternative currencies to Ignis such as MATIC, Ethereum, or USDC.

The Polygon and Ethereum community on the other hand, will have easier access to our cards, as they will find them on their chain, accessible from their accounts and with the currencies they are used to.

4. Effects on supply.

As explained above, the supply of each card remains unchanged, although cards can now live in two different blockchains. In particular, the supply of each card is as follows:

The Special Cards, Tarasca and Groostlang, has a supply of 250 copies each. They also exist in the Polygon chain and can be traded on OpenSea, but note that they distribute dividends only in Ignis, so you will prefer to keep them in this chain and swap to Polygon only to quickly trade them.

To verify at any time that the supply has not been inflated, it is enough to do the following operation for any card in the collection:

PBA=Total Supply — ABA.

In other words, the balance of the Polygon Blocked Account must always be equal to the card’s Total Supply minus the balance of that card in the Ardor Blocked Account.



Mythical Beings

Mythical Beings is an NFT card collection game. Every card and creature is unique and has an ancient story. You can collect, buy, trade, and craft cards.