Gleeok

Gleeoks are long-necked, armless dragons usually depicted with multiple heads. In many cases, the heads continue to operate separately from the body if severed, and are aptly called Heads of Gleeok. In most cases, removing all heads defeats the Gleeok. They first appeared in the original The Legend of Zelda and have made sporadic reappearances since.

The Legend of Zelda
In The Legend of Zelda, Gleeoks appear in various labyrinths with varying amounts of heads. Each head moves around, shooting fireballs. Link must attack the Gleeok several times to sever the heads, after which they become floating Gleeok heads. Once all the necks are severed, the Gleeok and its heads are defeated. In the First Quest, a two-headed one first appears as the boss of Snake, the fourth labyrinth. Later, a three-headed one appears as an enemy in Dragon, the sixth labyrinth. Finally, a four-headed one is the boss of Lion, the eighth labyrinth.

In the Second Quest, a two-headed Gleeok first appears as the boss of Level-2. A three-headed one is later the boss of Level-5. A two-headed one is an enemy in Level-6, and a four-headed one is the boss of Level-7.

The Legend of Zelda: Oracle of Seasons
In The Legend of Zelda: Oracle of Seasons, Gleeok is the boss of Explorer's Crypt, the 7th dungeon, where it guards the Seed of Life. It is found in a room with floor spikes making up much of the back corners. It can breath two consecutive spread shots of three fireballs, spawn four fireballs in a cross formation around Link, and drop a single fireball that splits into six small ones. Unlike most appearances, it has four legs. It also has two heads, and they now will reattach themselves if given time to. When both heads are off, they disappear, but the skeleton of Gleeok's body remains and tries to trample Link, alternating between jumping to stun Link with giant tremors and running in a straight line towards him until it bashes off the wall. After enough hits, Gleeok's remains are defeated.

The Legend of Zelda: The Minish Cap
In The Legend of Zelda: The Minish Cap, a lava-dwelling Gleeok named Gleerok appears as the second boss. Unlike most Gleeoks, it is only shown with one head by default.

The Legend of Zelda: Phantom Hourglass
In The Legend of Zelda: Phantom Hourglass, Gleeok, Two-Headed Dragon is the boss of the Temple of Ice. Depending on player choice, it can be the fifth or sixth boss, along with Dongorongo. It is the largest depiction of Gleeok in the series, though only its heads and necks are shown, with the rest being underwater. The head and neck on the player's left is red with antelope-like horns and capable of breathing fire balls, and the one to the right is blue with antlers and capable of breathing ice balls. The area Link stands to battle it is a small rectangle with a peg near each corner. Link must use the grappling hook on pairs of pegs to form a slingshot to deflect their shots into the other head, causing its mask to crack. When Link makes the slingshot, however, the one that made the shot will move close to the platform and slam its head down while chomping, which will get rid of the rope and can damage Link if he is too close. The red one will additionally make a second chomp for Link regardless. When they have been damaged three times total, they will quickly submerge, making a huge wave. Link must quickly jump atop one of the pegs to avoid it. Chunks of ice will also fall from the ceiling, and will damage him on contact. Link can run through the shallow water to avoid them, but will have to run against the current to make it to another peg. If he makes a tightrope between pegs beforehand, he can simply walk on it instead. After the chunks are all gone, the water returns to its normal depth as Gleeok resurfaces. After three more total hits, both masks will have been destroyed, and they will submerge again, starting the wave portion over. This time, a single larger ice chunk drops alongside the smaller ones.

When Gleeok resurfaces this time, each head destroys the peg closest to it. Now, one will move up close, slam its head a few times, and charge up a steady stream of their element. While inhaling, their looped tongues hang out and must be grabbed with the grappling hook and attached to one of the pegs, slamming them together and stunning it. This gives Link a chance to attack it with the sword repeatedly. After eight points of damage on each, they submerge yet again. The ice chunks that fall are now generally larger than before, with a few as big as the previous giant one. They surface yet again, and the process must be repeated. Eight more points of damage each will defeat a head, causing it to lull back and turn into sand, but retain shape until the other is defeated. Once both are defeated, two minutes are added to the Phantom Hourglass, and a large bridge leading to the room with the Azurine surfaces.

The Legend of Zelda: Breath of the Wild
Gleeok does not appear directly in The Legend of Zelda: Breath of the Wild, though Gleeok Bridge is named for it. It is located in a group with several other bridges named for bosses from the first game.

Link: The Faces of Evil
A three-headed Gleeok appears as a one-time enemy in Link: The Faces of Evil, found at the top of Spearfish Falls. It stole a necklace from Alora, and Link must defeat it to get it back. It launches two of its heads at Link by its own accord when he arrives.

Zelda: The Wand of Gamelon
Another three-headed Gleeok is a unique enemy in Zelda: The Wand of Gamelon, appearing in Dordung Cave. When it is defeated, it drops a Heat Crystal, which can be used to upgrade her sword.

Super Smash Bros. Brawl
In Super Smash Bros. Brawl, Gleeok appears as a sticker. It uses its artwork from The Legend of Zelda.

Cadence of Hyrule: Crypt of the NecroDancer featuring The Legend of Zelda
In Cadence of Hyrule: Crypt of the NecroDancer featuring The Legend of Zelda, a -themed Gleeok named Gleeokenspiel appears as a a boss.

Trivia

 * In the comic adaptation of The Legend of Zelda: A Link to the Past by Shotaro Ishinomori, Helmasaur Kings are incorrectly labeled "Gleeocks." This confusion likely stems from their similar Japanese name, Geekrock.