Gregal

Gregal is a member of the Wind Tribe who is plagued by an evil spirit. When Link fuses Kinstones with the Stranger in Hyrule Castle Town who turns out to be a Wind Tribe member, a warp portal to the Palace of Winds in the Cloud Tops opens up near Link's house in South Hyrule Field. Here, Link finds the bedridden old man suffering under the spell of a circling Rupee Wraith who slowly saps his will to live, and plans to kill him if given time. The only way to exorcise this vile apparition is to suck it into the Gust Jar; the ghost constantly moves about, making it tough to ensnare. If Link saves Gregal's life, Gregal will be found later, restored to full health, stretching and exercising in his home on the second floor of their home. Link will be rewarded with Light Arrows for his help.

However, there is a limited time window to do this. If Link ventures toward the Cloud Tops by way of Veil Falls before saving Gregal from the ghost, he will be informed that Gregal has died, making the Light Arrows unobtainable.

Trivia

 * Although Gregal's ghost is clearly visible to Link, no one from the Wind Tribe seems to see it; they act very surprised when Link mentions it later.
 * The ghost that haunts Gregal is the only Rupee Wraith to make an appearance in The Minish Cap.