A Grodus X is a protector of Grodus. Up to four of them can appear, and they will raise Grodus's defense for each one, making the battle extremely difficult. However, if all four of them appear, Grodus will be invincible. Mario should use any Shooting Star, Thunder Rage, or multiply-hitting items he has left to take these out.
Grodus X acts like Mini Yux, which form barriers to protect Yux. However, the Grodus X superficially resembles Yux more than their miniatures. 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).