When you buy a Hero on Marketplace, you must first "Redeem" it in order to use the Ascend feature. If you don't want to use that Hero for Ascending but only in-game, please sync to save your minting fee.
You go to Profile -> select "Heroes" -> select the Heroes you want to choose -> click Redeem -> click Confirm.
Press "Sync" to sync data. Heroes successfully purchased on Marketplace will show up in your Heroes inventory.
If you want to sell Heroes that have not been minted on the Marketplace, you must proceed to mint these Heroes into NFT Heroes. Including previously redeemed Heroes, and Heroes summoned from scrolls and shards.
To do this, go to the game and select the "Heroes" section, -> Select the Heroes you want to mint --> click "Mint" --> confirm the cost of mint, and press "Confirm".
Note: Heroes after redeeming, or summoning from scrolls and shards, can only mint NFT Heroes after 48 hours.