- Not to be confused with the island.
After battling off Garmadon's Stone Army, the Ninjas finally arrive at the Temple of Light where they harness their pure elemental powers, concentrating them onto Lloyd who becomes more powerful than he ever imagined.
Extended: The Ninja finally arrive on the Dark Island, where the Stone Army prepares for the final battle and Garmadon mines Dark Matter, the purest of Evil from the heart of the island, to build a Super-Weapon that can turn the tide of the war. Meanwhile, the Ninja learn that the Temple of Light is where they can both receive their elemental powers and where Lloyd can gain the skill of the Golden Dragon, a fighting style practiced only by the First Spinjitzu Master, after striking the 'Instrument of Peace'. The Tinkerer and Nya meanwhile builds the Ninja new vehicles: a drill-tank for Cole and a robot for Kai. As the Stone Army searches for them and Sensei Wu, Misako, the Tinkerer and Lloyd guard the hidden Bounty, the Ninja infiltrate Garmadon's camp and Zane finds and retrieves his falcon, with Jay locating the Temple while he is gone. Zane succeeds, but is spotted and the Ninja have to save him. Running from the army, they narrowly escape and go back to get the machines. The Ninja head for the Temple of Light, narrowly avoiding capture by the Stone Army. Inside the temple, they find murals depicting all their major victories, and they find a great bell hanging above a strange design on the floor where the Ninjas' symbols reside. Lloyd strikes the bell, the 'Instrument of Peace', and activates the power of the Temple, gifting the four Ninja with Elemental swords and kimonos. They then feed their power into Lloyd just as the Stone Army attacks, imbuing him with his full power. With their new powers, the Stone Army is defeated and the Ninja get ready to face the final battle. But the Celestial Clock is still counting down, and the Overlord tells Garmadon that when it reaches zero, there will be nothing to prevent Darkness from winning.
Having arrived at the Island of Darkness, the ninja stay hidden while the Stone Army is preparing for the final battle. On the Destiny's Bounty, the ninja learn that the Temple of Light is where they can receive their elemental powers, and where Lloyd can gain the Ultimate Spinjitzu Master technique: the Golden Dragon, a fighting style practiced only by the First Spinjitzu Master. To do this, the ninja must use a medallion to find the temple, where Lloyd must strike the Instrument of Peace. The ninja prepare to head out, but Sensei Wu tells Lloyd to stay behind—they cannot risk starting the final battle early, by having him encounter his father. The Master also tells his pupils to remain stealthy at all costs, as Garmadon does not yet know they are here.
Lord Garmadon oversees the army's mining of Dark Matter, pure evil in the heart of the island, to build a superweapon that can turn the tide of the war. Unbeknownst to the heroes, The Overlord has sensed the ninja's presence and tells Lord Garmadon to find them before they can reach the Temple of Light.
Dr. Julien and Nya begin building new vehicles for the ninja: a power drill for Cole and a robot for Kai. As the Stone Army searches the Island and Sensei Wu, Misako, Dr. Julien, and Lloyd guard the hidden Bounty, the ninja infiltrate Lord Garmadon's camp, only for Zane to rush off when he notices his Falcon. He retrieves it but is spotted by the Stone Army and the other ninja have to save him. Running from the army, they narrowly escape and go back to get the machines. On the bright side, Jay was able to find the Temple of Light by aligning three lights with the holes in the medallion—the temple is at the top of the Island's highest mountain.
With their new vehicles, the ninja head for the Temple of Light, barely keeping ahead of the Stone Army. Inside the temple, they find pictures on the walls depicting their journey from the past until the present. Further in is a great bell, hanging above a strange design on the floor bearing the ninja's symbols. Realizing that it's the Instrument of Peace, Lloyd strikes it, causing a light to shine on him and beams of energy to reflect off crystals in the walls. Soon, the entire room is crisscrossed with beams, and one hits a pillar, making it glow brightly. At the foot of the pillar, Kai's robes transform, and a dragon sword with the power of Fire appears in his hand.
In rapid succession, Zane, Cole, and Jay undergo similar transformations, regaining their powers over Ice, Earth, and Lightning, respectively. As their swords manifest blades representing their respective elements, Lloyd rises into the air. The ninja use their swords to send their elemental powers to Lloyd, who glows brightly as a Golden Dragon appears for a split second. When the light fades, Lloyd lands on the ground, wearing a new suit similar to the other four ninja, and with his true powers unlocked.
The Stone Army finally marches into the temple, but the ninja are more than ready for them—using their new elemental powers, they easily trounce the warriors. Kai beats up some soldiers within a ring of fire, Jay electrocutes a whole line of enemies with a single touch, Zane tricks a group of his foes into turning themselves into an ice pillar, and Cole swallows his opponents in a mound of dirt. Finally, Lloyd summons the power of the Golden Dragon, creating a brilliant light that frightens the remaining stone soldiers into retreat.
Lloyd's powers cause a Golden Dragon to appear on the roof of the Temple, roaring mightily. From the Bounty, Sensei Wu and the others celebrate, knowing that their friends have succeeded. Atop the mountain where the Celestial Clock resides, Lord Garmadon comments that the Stone Army isn't as invincible as they thought. The Overlord is unfazed, telling Lord Garmadon that their strength grows along with the ninja; the Ultimate Weapon will be completed just as the Celestial Clock reaches the end of its countdown. The Overlord assures Garmadon that the Ultimate Weapon will ensure that nothing will prevent the triumph of darkness, as the Celestial Clock's hands get ever closer to the skull emblem marking the time of the final battle.
- Cole - Kirby Morrow
- Dr. Julien - Mark Oliver
- Edna Walker - Jillian Michaels
- Garmadon - Mark Oliver
- Jay - Michael Adamthwaite
- Kai - Vincent Tong
- Kozu - Paul Dobson
- Lloyd Garmadon - Jillian Michaels
- Mini Scout - Vincent Tong
- Misako - Kathleen Barr
- Nya - Kelly Metzger
- The Overlord - Scott McNeil
- Warrior Scout #1 - Michael Adamthwaite
- Warrior Scout #2 - Vincent Tong
- Warrior Scout #3 - Paul Dobson
- Wu - Paul Dobson
- Zane - Brent Miller
- The Final Battle (mentioned)
- Celestial Clock
- Dark Matter
- Elemental Blades
- Earth Elemental Blade
- Fire Elemental Blade
- Ice Elemental Blade
- Lightning Elemental Blade
- Helmet of Shadows
For the transcript of the episode, click here.
- Zane's line, "I got us into this mess. I know how to get us out" took Brent Miller over a dozen tries before he got to the version used in the episode.
- The episode's opening scene is an homage to the beginning of the 1979 film, Apocalypse Now. The episode's title is based on that of the film's source novel, Heart of Darkness.
- After burying some of the Stone Army in the earth, Cole dances to the Ninjago version of Billie Jean by Michael Jackson, even saying "hee hee."
- This episode marks the first appearance of the ninja's new Elemental robes after their ZX were transformed into them, and their Elemental Blades serve as replacements of the Golden Weapons.
- The events of "Home" and "Day of the Great Devourer" are mentioned in this episode.
- The Temple of Light theme from when the ninja get upgraded at the Temple of Light is later used briefly in "Enter the Digiverse" when Zane becomes golden.
- This is the first episode not to feature Ninjago Island.
- When the ninja arrive at the foot of the mountain via Earth Driller, Zane is seen in his Elemental suit even though the ninja had not received them yet.
- When Lloyd reaches the top of the mountain, you can hear the gasp he makes when he was a kid (for example, in "Child's Play" when he realized the ninja were turned into kids).
- In the Temple of Light, Kai brushes dust off the floor, revealing the Fire symbol, but in the next wide shot, he is shown to be standing on the Earth symbol despite not moving to a different position.
- When Zane says "No one move!", he says it in Cole's voice.
- In the scene with Wu and Lloyd, after Jay asks if Lloyd was jealous, the iris of Lloyd's eye is yellow instead of the normal white color.
- When the Stone Army ambushes Wu, Lloyd turns a Stone Warrior to rock and a bird almost immediately defecates on its helmet. However, at the end of the scene, when the Stone Warrior is seen again, the bird feces can no longer be seen.
- At the end of the episode, Lloyd is wearing his ZX suit instead of his Elemental suit.
- When Lloyd refuses to stay in the Bounty, Misako has lighter hair that is obviously badly trimmed.
- When the ninja fall from the bridge, they use Spinjitzu to jump into the air. While this may seem like an error, The Curse of the Cat-Eye Jewel reveals another Spinjitzu technique developed by Nineko, Catjitzu, that allows the user to jump high.
For the gallery of the episode, click here.
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