Lasombra

"Oh, Arnold didn't tell you? We planned to go look for his precious green eyed people."

- La sombra revealing the deal he had with Arnold to Helga, Gerald, and the rest of the PS118 crew.

La Sombra is the main antagonist of the entire Hey Arnold series. He first briefly appeared in a flashback in the hour long Hey Arnold! episode "The Journal" and is the main antagonist of the 2017 TV film Hey Arnold!: The Jungle Movie. He is a river pirate who sought to steal the Corazon (a valuable ancient artifact) from the Green-Eyed People tribe and was successful until Miles and Stella Shortman stole it away from him. His ongoing quest to retrieve the stone came to fruition as he lures Miles and Stella’s son Arnold there while posing as their friend Eduardo under the pretense of helping Arnold find Miles and Stella, only to take him and his class hostage and threaten them all.

He is voiced by the famous actor Alfred Molina in The Jungle Movie, who also portrayed Maxim Horvath in Disney's The Sorcerer's Apprentice and Doctor Octopus in Spider-Man 2.

The Journal
La sombra appears briefly in the two part series finale.

As stated in "The Journal" La sombra was a greedy river pirate who stole the Corazon from the fabled Green-Eyed People for his own selfish purposes. What he didn't count on were a pair of adventurers named Miles and Stella Shortman. They were both successful in saving the Corazon from La sombra, who swore revenge.

Hey Arnold!: The Jungle Movie
La sombra returns in the 2017 television movie as the main antagonist. At one point, he disguised himself as Miles and Stella’s close friend, Eduardo, so that he could trick Arnold into leading him to the Corazon.

He is first seen watching Arnold from his computer screen and recognizing Arnold by his football-shaped head, he chuckles evilly to himself, realizing that his plan is working.

He is next seen on his ferry boat on the docks of San Lorenzo, disguised as Eduardo and pretending to be him by quickly recognizing Arnold. He invites Arnold and company aboard his boat and introduces them to his crew, one of which Olga falls in love with, much to the irritation of Helga G. Pataki. Once they sail down the river, La sombra/Eduardo sees Arnold's necklace glow and confirms him to be chosen by the green eyed people, according to the ancient prophecy. He proposes they find the green eyed people and find out the answer the Miles and Stella' s disappearance.

He then talks with Arnold about the threat of La sombra, and that he was not happy that Miles and Stella stole the Corazon from him. When Arnold says they are in danger, La sombra/Eduardo says that while they could turn around and head back to safety, they could also continue ahead and maybe find out about his parents. He then tells Arnold not to tell the others, under fear that they would get worried.

Later that night, wnile keeping lookout, La sombra/Eduardo is smelled by Abner, Arnold's pig. Abner doesn't smell anything good and tried to warn Arnold, but to no avail. He then decides to leave the ship so that he could warn Arnold's grandparents. Arnold then tells La sombra/Eduardo that a ship is following them, which turn out to be river pirates. He makes Arnold believe that La sombra is attacking them, and orders Arnold to stay down while he fights the pirates off and to forget about his friends. He then steers the ferryboat into dangerous rapids, confident that the pirates would not follow them through there. He succeeds in outrunning the pirates, at the cost of wrecking the ferryboat on some rocks.

The next morning, the wrecked ferryboat explodes, leaving Arnold, La sombra/Eduardo literally up the creek without a stinkin' paddle. He assures them that he will lead them through the jungle to his habitat.

When asked by Helga who attacked them and why, La sombra/Eduardo explains to the group of the river pirates threat, and their and La Sombra's vendetta against Arnold. Sid then asked why La Sombra is after Arnold, to which La sombra/Eduardo says it is only Arnold's buisness and leads the group into the jungle.

La sombra/Eduardo leads the group to his hideout. He then reveals to them, via taking off his fake moustache, that he is not Eduardo, but actually La sombra. He then proceeds to take everyone prisoner and reveals that he was the one who arranged the class trip to San Lorenzo to lure Arnold there. He then reveals to everyone that he and Arnold had a deal, that they would go look for the green eyed people, much to everyone's shock and anger. He then has his men lock the group and Arnold away.

Later that night, Arnold, with the help of Gerald and Helga, sneak past a guard and escape. La sombra isn't angered, however, as he put a tracking device on Arnold so he could lead him to the green eyed people, knowing they would show themselves in his presence.

As La sombra and some of his men pursue Arnold, he lets them die as a result of booby traps, intent on catching Arnold.

A short while later, La sombra arrives at the village of the green eyed people, and spots the Corazon with greedy eyes. He then reveals the tracking device on Arnold's necklace, using the green eyed people's own treasure against them in the process. He then shows surprise that the only green eyed people awake are children, and decides to take the treasures in the kingdom, and bring people there to sell it to them. He is then attacked by the Green-Eyed children, Gerald, Helga, and Arnold. He then breaks out, grabs Arnold, and flees the scene.

He then leaves Helga and Gerald to die hanging from a broken bridge, and forces arnold to open the Corazon's box or else they'll die, to which Arnold complies. Once the Corazon opens, La sombra pushes Arnold aside and tries to take it.

But before he can even touch it, the box shoots La sombra in the forehead with a poisonous dart, causing him to fall off the cliff and into the canyon. La sombra later climbs back up, his skin green from the poison. He then finds the real Eduardo and mocks his mustache. He then attacks Eduardo, trying to stab him with the dart from his head. But in the struggle, the Corazon is knocked down and rolled off the cliff.

Furious at losing the Corazon again, La sombra grabs Arnold by the shirt, and orders him to go and get it back. Before he could let Arnold go, the poison of the dart finally got to him, resulting in him staggering back. Before he falls, however, he grabs Arnold's amulet, and falls into the canyon to his death, ending his evil reign in San Lorenzo once and for all.

Quotes
"NOOOOO!!! You meddling do-gooder gringos! I’ll get the Corazon back if it’s the last thing I ever do!!"

- in "The Journal"

"So, you've heard about the infamous Lasombra? He was not happy that your parents stole back a precious treasure from him, the Corazon. (..) We could turn around and head back to safety or we could continue ahead, and maybe find out about your parents."

- A hint to Fake Eduardo's true nature.

"Now friends, let me explain what just happened back there. (...) Eh true, we have escaped an unexpected attack and yes our boat is unfortunately wrecked but there is good news, we are not lost, we can hike from here to our jungle habitat, a safe place."

- Lasombra leading Arnold and co. into his trap.

"May I have your attention? There's been a misunderstanding which I would like to correct. I am not Eduardo, I am La Sombra, and you are now my prisoners. And you will remain my prisoners until this football headed boy shows me where to find the Corazon!"

- Lasombra revealing his true colors.

"As you can see I've made a living stealing and selling all that is precious in central America, but one treasure still eludes me; The Corazon."

- Lasombra explaining his plan to steal the Corazon.

"Whats going on? (..) So, did a small child knock you out? Or did you just, fall asleep? (..) (laughs) Well done. You did exactly as I wanted. See? I intended for him to escape. The Green Eyes would not have shown themselves if I was with him, so I put a tracking device on him, now he will lead me straight to them. Gather the group, we're going hunting for green eyes! And their precious Corazon..."

- Lasombra plotting to go after Arnold after putting a tracking device on him.

"Eyes on the prize...."

- Lasombra after leaving some of his men to die going after Arnold.

"I know what to do. Buenos días, partner!"

- Lasombra after arriving at the Green-Eyed people's palace.

"I can see we're not wanted here, Arnold. ¡Vamonos! (...) No? I need you, parnter!."

- Lasombra fleeing with Arnold and the Corazon.

"Out of my way! So beautiful, and it's all mine...."

- Lasombra before being shot by a poison dart.

"So, you finally caught up to us, Eduardo. You call that a moustache?!"

- Lasombra coming back up for his final attempt to take the Corazon.

"You pest, just like your parents! I don't care if I have to throw you off the cliff, GO GET IT!"

- Lasombra's final words before succumbing to the poison and falling off the cliff to his death.

Trivia

 * His name means "The Shadow" in Spanish.
 * Lasombra turn out to be the central villain of the whole Hey Arnold series as he is responsible for the disappearances of Arnold's parents.
 * Much like Percival C. McLeach, he is a dark villain in a light adventure setting in a sequel that is set in an even more serious nature than the predecessor, Alphonse Perrier du von Scheck (though he does have occasional comical moments, even if most of it is dark humor).
 * When it was confirmed that Hey Arnold!: The Jungle Movie was cancelled due to the poor reception of Hey Arnold! The Movie, many fans got upset, because nobody knew what would have happened (including the fate of both Arnold's parents and La Sombra). But 15 years later, it was finally revealed that the movie will be on television in 2017.
 * La Sombra is the first and only villain on Hey Arnold! to die in the series.
 * He was also one of the 4 characters to die on screen. The other 3 were Angel the fish from "Eugene's Pet" who eaten up by a shark, Helga's Parrot from the episode by the same name that was eaten by a Monitor Lizard, and one of La Sombra's men who was used as a human shield against the Green-eyes' trap.
 * In a promotional image, La Sombra's hair was grey.
 * In a voice test of in 2014, La Sombra is seen wearing a red Aztec mask, the same as he wears in the journal. In The jungle movie, the very same mask can be seen on La Sombra's wall.
 * He is similar to Tamatoa from Moana, since they both covet a certain kind of treasure (Lasombra wants the Corazon and Tamatoa wants the heart of Te Fiti). But while Tamatoa was a comical villain, Lasombra was more serious than comedic.
 * He is also similar to Bill Sykes from Oliver and company. Both were greedy, both die near the end of their perspective movies, and both didn't care if their minions died, (In Sykes' case, Roscoe and DeSoto).