Building Challenge is a feature that allows players to combine lower-tier NFTs including heroes, skins and runes for a chance to get New Random NFTs at a Higher tier. players also have to use $ES as a fee before combining.
The number of NFT items and fees used for a building challenge will be different depending on the NFT type.
If players are using heroes as a material to combine, they must combine 6 NFT heroes and 20,000 $ES as a fee for combining. The reward will be 1 random rare NFT skin.
If players use skins as a material to combine, they must combine 6 NFT skins with the same rarity, and the $ES used as a fee for combining is determined by the rarity of each skin. The reward will be 1 random NFT skin at a higher rarity.
Lastly, as same as using skins, if players use runes as a material to combine, they must combine 6 NFT runes with the same level, and the $ES used as a fee for combining is determined by the level of each rune. The reward will be 1 random NFT rune at a higher level.
The graphic below illustrates the number of materials to be consumed, the number of $ES to be spent on a building for each material used and the returning rewards.