Egg-Blade

The Egg-Blade or Eggblade (エッグブレード, Egguburēdo) is a new and rare varity of Yoshi Eggs. It is a Yoshi Egg that transformed into a strong sword by of swallowing a rare sword-like item or a rare variaty of swordman species.

Background
It was said the Egg-Blades are very dangerous type of objects that are prohibited by the law of the Yoshis about 10 years ago prior the events of Super Mario Bros. X: Sea Side Adventure, due to the use of it would bring ruins. That law was made after there were a war between dinosaurs; the Yoshis, the Rexes and the Reznors. There was a young Yoshi who wielded the Egg-Blade, but didn't knew how. By using it without having any idea how to use it caused an immense cyclone over the region, which stopped the war but left the dinosaurs very injured. Sometime later, the Yoshis made the law to never use or create an Egg-Blade, and to make the possibility to create them ceasing to exist, just until the day Yoshi was the second one to use it since he came to Sea Side's land of the Yoshis. Learning that Yoshi was the only one to be able to use an Egg-Blade, the Yoshis chose only him to use one except others.