From the Super Mario Wiki
Earth Link is a giant mechanical snake that lives in Smithy's Factory in Super Mario RPG: Legend of the Seven Stars. The snake is the pet of Cloaker, the sword and shield-wielding jester who is also a member of the Smithy Gang. Earth Link attacks by poisoning his enemies.
As Mario and his friends travel through Smithy Factory, they encounter a strange pair of villains named Cloaker and Domino. The jesters are determined to stop the heroic plumber, and challenge Mario to a fight. In battle, if Mario and his allies defeat the magic-wielding Domino first, Cloaker will retreat to his pet, Earth Link, and electronically fuse with the huge snake. However, even with their combined power, Earth Link and Cloaker are no match for Mario's party. As such, the jester and his pet are quickly defeated.
Earth Link is a palette swap of Mad Adder, Domino's snake.
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