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Tekkyū Dosun are spiked balls on chains that appear in Super Mario World 2: Yoshi's Island, its remake Yoshi's Island: Super Mario Advance 3, and Yoshi's New Island. They typically appear in castles and forts.
Tekkyū Dosun is wound up by a Boo Guy that sits in the wall. Once it is wound up as far as it will go, the Boo Guy will let go and the heavy ball will drop. If the ball touches Yoshi, Baby Mario will fall off Yoshi's back. The Boo Guys take some time to wind up the maces, giving Yoshi time to safely pass underneath. Tekkyū Dosun, as well as the Boo Guys that operate them, are invincible.
In Yoshi's Story, similar objects appear alongside Ball 'N' Chains in The Tall Tower and Magma Castle. Unlike the Yoshi's Island games, they are not operated by a Boo Guy, and there is a pause before they drop down. They also have the same appearance as the game's Ball 'N' Chains.
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