The Building Challenge is a unique feature that gives players the opportunity to upgrade their lower-tier NFTs, including heroes, skins, and runes, into higher-tier ones. This process involves combining multiple NFTs of the same type, along with the payment of a certain fee in $ES, the secondary token. The precise quantity of NFTs and the fees required for a building challenge depend on the type of NFT involved.
If skins are used for the challenge, the players must combine 6 NFT skins of the same rarity. The $ES fee for combining depends on the rarity of the skins used. The reward will be 1 random NFT skin of a higher rarity.
Much like the skins challenge, when players use runes for the building challenge, they must combine 6 NFT runes of the same level. The combining fee in $ES depends on the level of the runes used. The reward will be 1 random NFT rune of a higher level.