Watergleam

The Watergleam is an key item in Kingdom Hearts.

Although it's unknown what is Dumbo's world was it is noted that the Heartless swallowed his world and he was transformed into the Watergleam summon gem and eventually landed in Monstro's body. Sora can find the Watergleam in Monstro after obtaining High Jump. Upon taking it to the Fairy Godmother, Sora can learn the ability to summon Dumbo.