Iron Ball

are recurring traps in.

In, Iron Balls can be found inside Ancient Shrines. They appear rolling down ramps and can damage Link on contact or by pushing him into the void. Link can stop their movement with Stasis. By using Magnesis, Link can move the Iron Ball around and use it as protection from incoming Boulders.

The Legend of Zelda Game Watch
In, Iron Balls can be found in dungeons. They can only be defeated with the Boomerang. Once they are defeated, Link can obtain the Sword required to defeat Bats.