Aavegotchi ERC721 NFT manages an escrow contract address that holds their token. Currently, only aToken (from Aave) could be used as Spirit Force.
yToken (From yEarn) are also yield-generating token (yDai, yUSDC, yUSDT, yETH, yCRV..and more) and are wlidly use in the DeFi community.
The goal of the proposal is the vote for the use of yToken as Spirit Force.