From the Super Mario Wiki
The Magma Castle is the front-right fort on Bowser's Castle in Yoshi's Story. This is often considered to be the hardest of the castle levels, and it is where lava is transported through Bowser's Castle. It is also the storage facility, as many rare creatures are located here such as Spikes, Puffers, Barbecue Guys, Attacky Sacks and even a red dragon. A Slug also thrives in the depths of the tower.
The Yoshis found the castle and figured the Super Happy Tree was there. Instead they found hot lava and a hot-tempered Baby Bowser. But happiness wins in the end, and the Yoshis battled Baby Bowser.
Names in Other Languages