Cobalt Star

The Cobalt Star is the name given to the power source for Professor E. Gadd's time machine in the game Mario & Luigi: Partners in Time. The Cobalt Star was shattered into multiple Cobalt Shards by Princess Peach after she used it to trap Elder Princess Shroob, the leader of an alien race that was invading the Mushroom Kingdom of the past. Destroying the star also caused Time Holes to appear between the past and present, and with the help of their infant selves, Mario and Luigi go about retrieving the shards and reassembling the Cobalt Star to fix the fabric of time and save Peach from the aliens. Baby Luigi and Kylie Koopa both realize something is amiss with the Cobalt Star, however the full truth is not revealed until it is too late: all of the Shards are assembled and Elder Princess Shroob uses her regained power to break free of her prison and attack the heroes.

It is unknown if the Cobalt Star was destroyed, or if it simply shattered into pieces again (although Elder Princess Shroob says, right after being freed, that the Cobalt Star "is no more").

Cobalt Shards
The six shards of the Cobalt Star are what Mario and Luigi are trying to collect. Their locations are:
 * 1) In Bowser's Castle
 * 2) In the possession of Swiggler in Vim Factory
 * 3) In the possession of Petey Piranha in Gritzy Desert
 * 4) In Star Shrine
 * 5) In the possession of Toadbert, at first at Yoshi's Island, later at Star Shrine.
 * 6) In the possession of Princess Peach at Shroob Castle