The Star Rod is from 'Paper Mario 64'. This item was stolen from 'Star Haven' by Bowser and gave him the ultimate power of invincibility. When powered by the Star Rod, Bowser had a rainbow hue around him, and attacking him only led to the "dink!" sound effect and no damage. In the end, the power of all of the Star Spirits plus Princess Peach's wishes gave Mario the power he needed to overcome the might of Bowser and take away his invincibility. During the final battle, he could also use the star rod to heal 30 of his HP or attack both Mario and his partner.