As far as I know, thetan arena offers free play to earn game but the rewards are low. You have to buy NFT heroes in order for you to earn more daily and have exclusive perks. The game play was easy and you can learn it within hours. The NFTs however isn't that pricy compared to axie. You can check them out.
It means that there is nothing extraordinary in the thetan arena other than just wasting time and energy when playing games, and for Axie I think that token will soon become a benchmark for others where now there are several tokens whose concept is also almost the same as Axie