Hyena is a white or light gray Weimaraner. In the anime, he is a darker gray with a white muzzle and brown eyes and he wears a red collar. He has odd eyelashes most prominent in the manga.
Hyena is very timid and cowardly dog, rising a question why he was accepted into the pack. Possibly he was with Sniper before joining the pack and was accepted with him. Hyena is distrustful of humans, because his owner abandoned him. He is Sniper's loyal minion, though seemingly out of fear. However, he speaks to the Dobermann in respectful way. Being his minion and ordinary pack member, he is able to walk among other soldiers and thus uses Hyena as a spy. At first, Hyena works for Sniper. Most dogs don't like him that much, but Ben tells them to accept him as their pack member, even though he is disrespectful towards Ben at the times. Hyena is cunning and seems to be a good liar, if he just doesn't start to panic too much. That's probably what he is best at as he is a poor fighter. Sometimes, though, he may try to fight if he has Sniper or other strong fighter on his side. He is also ready to kill if Sniper orders him to. Hyena starts to dislike Sniper as he realizes how less he cares about him and often sends him in danger. After getting saved by John, he tries to befriend him but the other dog isn't interested. Hyena also cheers for the other dogs during the battle and tries to fight with them, hinting that his attitude has changed a bit. Hyena stars to like the company of the other dogs, showing real loyalty and sometimes joking. He also shows his sensible side as he talks sense to the other dogs at the times.
Hyena starts to show worry about the other dogs and dislike traitors, attacking Terry when believing that he betrayed them. When finding the truth, he apologizes. He fights with the others against Kisaragi's soldiers and then is ready to face the bears, showing that he has became more brave. However, he has trouble to face Sniper and is afraid, but eventually does so. Hyena seems to have love for food. Before the battle against bears, he went to eat honey so that he could die with full stomach.
Like shown in the flashback of Ginga Densetsu Weed, after winning his fear he also bravely turns against Sniper and speaks back to him for the first time. He bravely sacrifices himself but remarks that he is no true hero, possibly thinking so because of his past. He also says that he doesn't want to be alone in the afterlife.
After Gin comes back with the other dogs to see Riki and and join the army of dogs, Hyena warns Sniper that if Gin is his son, Riki is sure to put him in charge instead of Sniper. Sniper relizes this is true and orders Hyena to keep an eye on Gin. Hyena and the dogs soon set off.
Betraying and rejoining the pack
After the dogs meet the three kai brothers. Hyena betrays Ben's platoon and meets up with Sniper, who kills a dog named Lloyd. Gin and Smith witness this and Hyena and Sniper chase them through the forest but eventually lose them. After Sniper learns that Ben survived the rock attack caused by Moss, he orders Hyena to rejoin the pack for more information. Hyena follows the pack from a distance for awhile, but is eventually caught after he is tormented by the Kōga Clan. The pack hears Hyena's cries and find him close by. The pack questions if Hyena should be killed for his betrayal, after some debate on who should kill him, Ben attacks Hyena but lets him live, much to Hyena's relief. After this, the Kōga clan shows up again, and the pack races off, leaving Hyena behind. Soon, Hyena begins to follow them again until he runs into John. In the manga, Hyena is captured by some members of the Kōga clan and is saved by John, while in the anime he is simply following the pack. Hyena is seen by Smith and the others during the battle with the Kōga clan, but is seemingly forgiven by them and returns to the pack. During this time, Hyena betrays Sniper and becomes more friendly toward the pack. Hyena is later seen trapped in the sand pit with Ben's pack, held there by the Four Heavenly Kings Of Mutsu and their pack of dogs. Hyena and Ben's pack watch as Terry, a dog who pretended to betray the group, is killed trying to help them. Gin shows up and and the dogs are able to escape the pit due to the rain. The two packs of dogs side together and are able to win a battle against some of Akakabuto's bears and earn roughly three hundred new warriors for the battle against Akakabuto. Hyena returns with the rest of the pack one night before the final battle.
When the final battle is near, Hyena is ready to face Akakabuto and his bears and wants to prove his courage to others. Before the battle starts, he sneaks away to get honey from a beehive, because he wants to die with a full stomach. Hyena sees Sniper, who he thought was dead, and sees how the Doberman fights Ben at the cliff. Ben throws both himself and Sniper down the cliff. Hyena runs up to the cliff and mourns over Ben, stating how much of a coward he is. Hyena hears Ben's howl and realizes he's still alive. He gets some courage and jumps down the cliff to save him. Hyena, Ben and Sniper all fell into a raging, flooding river. Hyena attacks Sniper and rips him off of Ben. The scene ends here, but continued later in the flashback scene of Ginga Densetsu Weed.
Hyena is notably more cowardly in the anime than in the manga. In the final battle, he is the only dog to hide instead of facing Akakabuto. Later, Hyena witnesses Ben throw both himself and Sniper down the cliff. He mourns over Ben and gets courage. He then jumps down the cliff, shouting Ben's name. He did not hear Ben's voice like in the manga version and thought he was dead, so this scene implies that Hyena committed a suicide.
Sniper mentions Hyena and a flashback is shown retelling the events of Hyena saving Ben from drowning.
Hyena managed to get out of the river and pulled Ben on the ground, thus saving his life. However, Sniper got out of the river as well. Hyena finally spoke back to him and told him he had changed and refused to serve him anymore. Hyena didn't have enough fighting skills to defeat Sniper in a battle, so he decided to sacrifice himself by pushing both himself and Sniper back into the water. Sniper then seem to kill Hyena by cutting his stomach open while they're underwater.
Hyena now known as Noah had survived confrontation with Sniper and was rescued by a fisherman who became his new owner.
- Hyena's breed is mentioned in Shounen Jump, as shown in this tweet.
- Yoshihiro Takahashi didn't like the character at all first because of his cowardly nature, but started to like Hyena after he became braver.
- Hyena is more important in the manga than in the anime, as he appears in more scenes in the manga, and has more dialogue in the manga altogether.
- Hyena appears as a spirit in GDW, making many believe he was confirmed dead till he returned as Noah in GDN.
- Hyena only appeared in Weed's eye as a ghost in the GDW Anime.
- For a scene sheet on a closeup on Weed's eye in episode 26, Hyena's name is misspelled as Haiena in rōmaji, that is the litteral spelling of his name in katakana.