Thorn

A row of Thorns.

Thorns, or Crystals are spiky obstacles found in Super Mario World 2: Yoshi's Island and its sequel Yoshi's Island DS. They are found mostly in castles. Contact with them will immediately defeat a Yoshi, making them very dangerous. Luckily, a Yoshi Egg destroys a single thorn, but since thorns are usually found in groups and Yoshi can only carry six Yoshi Eggs at a time, most thorn groups are impossible to destroy. However, in Yoshi's Island DS, Baby Donkey Kong's explosive eggs can easily destroy a group of them in one shot. Sometimes after they are destroyed, the thorns reveals Winged Cloud, and in The Potted Ghost's Castle, one specific thorn even reveals a door.