Star Rod (Paper Mario)

The Star Rod is a magical rod that can make all wishes come true. According to Russ T., ancient magic created the Star Rod long ago. In the intro of Paper Mario, Bowser breaks into Star Haven, steals the Star Rod, and captures as well as imprisons the seven Star Spirits, triggering the events of the game. He then uses it to grant all his evil, selfish wishes.

When Bowser battles Mario after usurping Peach's Castle, he uses the Star Rod to make himself invincible so that Mario's attacks are ineffective against him, which in turn allows Bowser to easily defeat Mario. Subsequently, Bowser uses the Star Rod to summon a bolt of lightning to blast the now-unconscious Mario out of the castle. After being revived by the projections of the Star Spirits, Mario must embark on a quest to save each Star Spirit.

In the first of three rounds of the final battle against Bowser, the Koopa King uses the Star Rod to power himself up. In this state, Bowser's attack powers are doubled. Mario can use Star Beam, bestowed upon him after having rescued all seven Star Spirits, to counter the effects of the Star Rod. In the final two rounds, Bowser is aided by Kammy Koopa, who activates the Power Platform to enhance his power so that when Bowser again uses the Star Rod to power himself up, Star Beam is unable to negate its effects anymore. With help from the Star Spirits, Princess Peach, and Twink, Star Beam is upgraded to Peach Beam, which is powerful enough to cancel the effects of the Star Rod once again. During the final battle, Bowser uses the Star Rod for the following moves:
 * Shockwave Drain (Boost loss for Mario and his partner)
 * Lightning Blast
 * Power Up (Doubles Bowser's attack powers; can be negated by Star Beam in the first round, Peach Beam in the third round)
 * Recover (20 HP in the first round, 30 HP in the second and third rounds)

After Mario finally defeats Bowser, he takes back the Star Rod and subsequently returns it to the Star Spirits. The Star Spirits then use the Star Rod to bring peace to the Mushroom Kingdom.

Unused graphics for the Star Rod are present in Paper Mario: The Thousand-Year Door, with an updated design.

Trivia

 * Despite being said to make him invincible, the Star Rod doesn't actually make Bowser invincible. It merely raises his defense by a substantial amount. With an attack that does at least 15 damage, it's possible for him to take damage while "invincible".
 * This also applies to the battle right before the final battle. It simply raises his defense from 1 to an unpiercable 4.
 * In Paper Mario: The Thousand-Year Door, a random Toad who appears in the Excess Express after Chapter 6 asks Mario "What did Bowser steal in the first Paper Mario?" to which the answer is "Star Rod".