Dragon Ball Z: Wrath of the Dragon

Tapion sealed himself inside the enchanted music box because he contains half of the monstrous Hirudegarn within his own body. One thousand years ago, Tapion and his brother Minotia used magical ocarinas to seal the two halves of Hirudegarn inside themselves, then sent the music boxes to opposite ends of the universe to keep the monster contained.

The elderly man who gives the box to the Z Warriors warns that Tapion is their only chance to stop the approaching evil.

Hirudegarn was split into two halves and sealed inside different containers one thousand years ago. When Shenron opened Tapion's music box, only the upper half was released initially. The lower half later manifested separately in the city, attacking before eventually reuniting with its upper half to form the complete monster.

Tapion reveals he only has half of Hirudegarn sealed inside him.

Hirudegarn is intangible and cannot be damaged by conventional attacks until it initiates an attack itself. This unique property makes the creature nearly invulnerable to physical blows, forcing the heroes to adapt their strategy during the initial confrontation.

Gohan and Videl discover through trial and error that their attacks pass through the monster without effect.

The ocarina is one of two magical instruments forged by a priest one thousand years ago specifically to combat Hirudegarn. When Tapion plays it, the haunting tune disrupts the monster's form and weakens it temporarily, causing Hirudegarn to vanish until the magic wears off.

Tapion's origin story explains the ocarinas were created specifically to seal and control Hirudegarn.

Tapion and his brother Minotia both sealed half of Hirudegarn inside themselves to stop the monster from destroying all life. While Tapion survived and remained sealed in the music box, Minotia's fate is not explicitly shown in the film, though the timeline suggests he either died or was lost somewhere in the universe during the sealing process.

Tapion mentions his brother helped him seal the monster.

Hoi claims that Tapion himself is the true threat, not Hirudegarn. He attempts to steal the ocarina, presumably to use its magical properties for his own purposes, though the exact nature of his plans remains unclear. Trunks ultimately stops Hoi and chooses to side with Tapion.

Hoi appears early in the film, establishing himself as an antagonistic figure with unclear motives.

Tapion believes that if he dies, the half of Hirudegarn sealed inside him will also be destroyed, permanently weakening the monster. He pleads for death as a desperate attempt to seal Hirudegarn again, but the creature escapes before they can carry out this sacrifice.

Tapion's isolation and reluctance to interact with others stems from his fear of accidentally releasing the monster.

Goku transforms into the legendary Super Saiyan 3, a form that dramatically increases his power beyond Super Saiyan 2. He then uses the Dragon Fist technique, channeling his ki into a powerful concentrated attack that pierces through Hirudegarn and defeats the monster completely.

The movie's description mentions Goku must quickly master a new technique to stop the revived evil.

After Hirudegarn is defeated, Tapion uses Bulma's time machine to travel back to his home world. He leaves Trunks the enchanted sword as a farewell gift, a weapon forged one thousand years ago to battle the monster.

Bulma's lab and technology are established earlier when Tapion reveals the backstory.

Goten and Trunks fuse into Gotenks 3 to participate in the final battle against the fully reformed Hirudegarn. Gotenks engages the monster in combat alongside Goku as Super Saiyan 3 and Vegeta, contributing to the combined assault before Hirudegarn temporarily defeats them.

Gotenks' fusion is a signature move in Dragon Ball Z that typically appears in major battles.