From the Super Mario Wiki
The Star Shrine is an area accessed from the top of Star Hill in Mario & Luigi: Partners in Time. Mario, Luigi, Baby Mario, and Baby Luigi come here looking for Cobalt Star Shards, the last two, to be exact. The place has many stars floating in space, and is similar to Star Hill. A living, star-shaped gate also resides here.
Elder Shrooboid, the boss of this area, Shroobifies Toadbert and Kylie Koopa during events captured in this area. Mario and company defeat Elder Shrooboid and get the last two Cobalt Star Shards here.
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