Magic Eggs are the official currency of Springfest, which had only been active once, in 2018. They can be used to purchase items in Fox Faction (Fort Fox) and Bunny Bandits (Bunny Burrow) stores for furniture, a unique buddy, or rare equipment only obtainable during Springfest. These can be obtained only during Springest from battles
"These magical eggs are only found when the Springfest is active. They can be collected by adventuring or performing Springfest activities. Spend them at the Fox or Bunny shops."