Thorn

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 kill a Yoshi, making them very dangerous. Luckily, a Yoshi Egg will destroy a single thorn, though 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 a cheat does exist for Yoshi to make some room by firing an egg to be able to land on the floor and then use a few Green Watermelons to destroy a row. However, in Yoshi's Island DS Baby Donkey Kong explosive eggs can easily destroy a group of them in one shot. Sometimes after destroyed the thorns reveals Winged Cloud, and in The Potted Ghost's Castle one specific thorn even reveals a door.