From the Super Mario Wiki
Grodus Xs are the protectors of Sir Grodus. Up to four of them can appear, and they raise Grodus's defense for each one, making the battle extremely difficult. However, if all four of them appear, Grodus is invincible.
Grodus X acts like Mini Yux, which form barriers to protect Yux. However, the Grodus X superficially resembles Yux more than their miniatures and can also cause damage. Though a Grodus X is small like a Mini Yux, its overall shape looks like a Yux with only stumps in place of arms and its the same color of green as Yux. Grodus X's single eye also looks like a Yux's, though Yux themselves have two eyes (as do Mini Yux, though theirs look different).
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