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Oh this doesn't look good
All three Hyudoros at their perfect form above Sonic the Hedgehog.
First appearance

Sonic & Knuckles

in other media
Biographical overview


Physical description



Black blank eyes.

Alignment and character traits


Powers and abilities
  • Invisibility.
  • Attacking in the dark.

Hyudoros (ヒュードロ Hyū doro?) are ghost enemies which first appear in the second act of Sandopolis Zone in Sonic & Knuckles. They are ghosts of beings that were trapped inside of capsules. They are freed by the player at the beginning of the second act and start to attack him as the zone gets completely dark.


Hyudoros are ghosts with a horrific appearance that usually exist in dark and ghastly places; for example inside the pyramid of Angel Island. In Sonic & Knuckles, it is possible that Hyudoros might be ghosts of starving animal friends inside the single capsule. These ghosts appear in three different forms, depending on how dark it is. The darker the act becomes, the stronger the Hyudoros will be:

  1. In full light, there are no Hyudoros.
  2. In semi-brightness, one small Hyudoro appears to be floating above.
  3. In semi-darkness, two evil-looking Hyudoros appear floating above, however they still don't start to do anything.
  4. In complete darkness, three Hyudoros with horns on their heads appear and start to attack the player.

Game appearances

Sonic & Knuckles

In Sonic & Knuckles, the player encounters the Hyudoros in the second act of Sandopolis Zone, after the player opens a capsule. Hyudoros cannot be destroyed; if the player jumps, they follow him. If the player goes too fast, they disappear and meet him wherever the player is. They don't try to hurt the player until it is completely dark. The player also can't touch them as they fly above until they are in their perfect form.

Well finally these guys got tired

The light switch on the roof.

The only way to make the Hyudoros disappear for a while is to pull down the light switches located around the level. The Hyudoros disappear completely and the lights go on when the player falls into the arena where the boss of zone is encountered. They can disappear if the player spins while the Hyudoros are attacking, but they  reappear a second later and continue their assualt. If the player is invincible then a similar effect will occur.

As Knuckles the Echidna, the ghosts seem to already be free, since Sonic opened the capsule earlier. This is especially dangerous at the beginning of Act 2, since the act starts off completely dark and Knuckles has no rings.  Hyudoros act identically throughout the entire act until the player gets to the boss arena.

Sonic Rivals 2

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A Hyudoro chasing Sonic and Rouge at Mystic Haunt.

After many years, Hyudoros reappear in Sonic Rivals 2. They appear as enemies at the Mystic Haunt, but this time only one Hyudoro appears, during one mansion section of the level. The player might not be able to defeat the Hyudoro himself but it is possible to make it disappear by pressing down the button before Hyudoro attacks.

The boss of the Mystic Haunt appears to be big variation of Hyudoro with horns, piloted by Eggman Nega. It is referred to as the "Egg Phantom". Like normal Hyudoros, its weakness is revealed to be the light.

Apperances in other media

Sonic the Comic

Sandopolis Ghosts (Hyudoros)

Sandopolis Ghosts as they appear in Sonic the Comic's issue 48.

In Fleetway's Sonic the Comic, Hyudoros are mentioned as Sandopolis Ghosts, and only appear in the issue 48 story Mystery of the Sandopolis ZoneCaptain Plunder, Filch and the Per'fessor attempt to leave the pyramid with several bags full of its treasure. Sonic tries to chase them, but Knuckles stops him, knowing the hazards of pyramids. As the place gets dark, small ghosts starts to follow Plunder and the others. Filch sees the ghosts and tries to warn Plunder and Per'fessor, but they don't see them. After that, three ghosts appear in front of them. Filch believes them to be "the wrong sort of ghosts", and the leering phantoms chase the pirates out of the pyramid, which seals shut behind them.

The Sandopolis Ghost has a slightly different appearance compared to its game counterpart, as it normally appears to be small blob, but it eventually develops a more sinister look and a full body of cloaked phantasms with arms.

Archie Comics

The Hyudoro were first mentioned in Sonic Universe #63 by Knuckles, who had previously encountered them. However, he noted that they weren't as aggressive as the ghosts of Pumpkin Hill Zone.


  • As the Sonic Jam strategy guide states, Hyudoros weren't created by Dr. Eggman. It also reveals that Eggman infiltrated into the pyramid and trapped the ghosts inside the Capsule, working very hard.
    • Several media mentions that Sandopolis Zone Act 2 takes place in a cursed pyramid, with Dr. Robotnik trying to trap Sonic inside.
  • When the capsule is opened inside of pyramid, it releases six Hyudoros even though only three of them start to follow the player. It is unknown where the three others have gone, although it is possible that as one of Hyudoros disappear, another one comes to take place.
  • Hyudoros and Boos are considered to be separate ghost species, but there are a few similarities. Both of them have resided in a dark pyramid and are able to disappear and come back.


Sonic the Hedgehog 3 & Knuckles

Main articles (Sonic 3 | Sonic & Knuckles | Sonic 3 & Knuckles) | Sonic 3's Gallery | Beta elements | Sonic & Knuckles' Gallery

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