Hydra enemy line

The Hydra, Aqua Hydra, and Pyrodra are species of monsters randomly encountered in Golden Sun: The Lost Age and Golden Sun: Dark Dawn. These monsters, resembling large three-headed sea serpents, are palette-swapped variants of each other that appear in different, mutually-exclusive locations within the same game. They also have differing levels of strength and similar-yet-different sets of battle skills, with the more dangerous variants typically appearing later in a game. This monster line includes one boss in The Lost Age, although it is demoted to a common enemy in Dark Dawn.

Aqua Hydra
The Aqua Hydra is a giant-sized variant with light blue scales and a light-green underbelly, and is a boss in Golden Sun: The Lost Age. It is a mandatory encounter in the beached Lemurian Ship located at the East Indra Shore. After Piers has joined the party, players are to eventually return to the ship and explore it, fighting Aqua Jellies along the way. In a room with a bunch of crates and six Aqua Jellies around them, interacting with the Jelly standing on one of the crates in the center causes the other five Jellies to suddenly, simultaneously jump into the first. The six Aqua Jellies then merge and metamorph into the single Aqua Hydra, which then immediately engages the party as a scripted boss encounter.

Many of the Aqua Hydra's possible commands are Mercury-based, and it has a Mercury Power rating of 115. The battle commands available to the Aqua Hydra include:
 * Attack: Used 28 out of 256 times, this is the monster's standard physical attack.
 * Raging Flood: Used 88 out of 256 times, this is a Monster Skill where the monster summons a wave of water from behind itself to wash through the player's party (this visual is similar to that of the Dreamtide Unleash of the Pirate's Sword). This is a Mercury-based attack with a base power of 110 that hits every party member. Unlike most forms of offense in the game, this attack always hits every character with an equal amount of force. This is perhaps the Aqua Hydra's most dangerous ability.
 * Triple Chomp: Used 53 out of 256 times, this is a Monster Skill where the monster bolts forward and strikes a single party member with three strong blue-colored bites in a row. This is a that deals approximately 2.4 times as much damage as a normal physical attack would.
 * Rising Venom: Used 35 out of 256 times, this Monster Skill has the monster lob a small amount of glowing green poison at a single party member. This is a Mercury-based physical attack that deals approximately 30 points more damage than a normal physical attack would. There is also a chance that the target will be Poisoned.
 * Drench: Used 29 out of 256 times, this is a Psynergy technique that drops moderately large spheres of water onto the opposition, dealing a Mercury-based attack with a power rating of 60 and a range of 3 targets. This ability consumes 10 of its user's Psynergy Points, meaning that the Aqua Hydra is able to use Drench exactly seven times throughout the battle. This move is actually much less damaging than Raging Flood, and likely exists only to give players somewhat of a break from its constant use of that Monster Skill and make the boss a little more manageable.
 * Slaver: Used 23 out of 256 times, this is a Monster Skill where the monster projects out of its mouth a lot of multi-colored saliva all over the player's party ("Slaver" may be a corruption of "saliva" that occurred during translation of the game). Each affected character may have his or her Defense rating temporarily lowered by 12.5%, down to a minimum of 50%. In other words, it works exactly like the Debilitate Psynergy, but has a range of 5 targets instead of 3.

This can be quite a challenging boss due to both its powerful full-party offenses and its large amount of HP. The Aqua Hydra is vulnerabe to Mars-based attacks, so the most obvious tactic is to have Jenna pound away with Djinn, Summons, and/or her strongest Psynergies, such as Fume and Beam. On the other hand, the Aqua Hydra's Raging Flood technique can make short work of an unprepared party, so a more defensive strategy may be preferable. At this point in the game, Jenna is the only party member who learns group-healing Psynergies in her default class, and even then she can only use them if she has at least four Mars Djinn set. Fortunately, there are exactly four Mars Djinn available at this point (Cannon, Spark, Kindle, and Char), granting Jenna access to the Aura Psynergy series. If she is at least level 16, her Healing Aura will prove invaluable for keeping the party alive. Alternatively, if you would rather or are willing to use a non-default class setup, assigning another character to a class with the Wish Psynergy series would free Jenna up for offense. On that note, summoning Meteor (which would require all four Mars Djinn) will deal around 800 points of damage to the Aqua Hydra in a single blow. Also, this battle would be a good opportunity to use up any Oil Drops you may possess, since they are essentially free Flare Storms that can be used by any character (preferably anyone besides Jenna, in this case).

Hydra
A Hydra is a normal-sized variant with purplish-pink scales and a light-orange underbelly. In Golden Sun: The Lost Age, they are among the "stock" monsters fought all throughout the Great Western Sea while sailing, as well as when sailing in the Northern Reaches.

Hydras have access to the following battle commands:
 * Attack: Used 4 out of 8 times, this is the monster's standard physical attack.
 * Triple Chomp: Used 2 out of 8 times, this is a Monster Skill where the monster bolts forward and strikes a single party member with three strong blue-colored bites in a row. This is a that deals approximately 2.4 times as much damage as a normal physical attack would. Hydras use this with a Mercury Power rating of 115.
 * Slaver: Used 2 out of 8 times, this is a Monster skill where the monster projects out of its mouth a lot of multi-colored saliva all over the player's party. Each affected character may have his or her Defense rating temporarily lowered by 12.5%, down to a minimum of 50%. In other words, it works exactly like the Debilitate Psynergy, but has a range of 5 targets instead of 3.

Hydras are the slowest monsters in the regions they are found in, and are moderately sturdy but are far outperformed in this field by Turtle Dragons. In other words, Hydras are not a very threatening enemy, statistically speaking. The only thing to really worry about is the occasional Triple Chomp for massive damage.

Pyrodra
A Pyrodra is a normal-sized variant with pink scales and a light-blue underbelly. In Golden Sun: The Lost Age, Pyrodras are among the randomly-encountered enemies fought throughout the deeper, tougher portion of Treasure Isle.

Pyrodras have access to the following battle commands:
 * Attack: Used 3 out of 8 times, this is the monster's standard physical attack.
 * Triple Chomp: Used 2 out of 8 times, this is a Monster Skill where the monster bolts forward and strikes a single party member with three strong blue-colored bites in a row. This is a that deals approximately 2.4 times as much damage as a normal physical attack would. Pyrodras use this with a Mercury Power rating of 115.
 * Fire Breath: Used 2 out of 8 times, this Monster Skill has the monster generating a mass of fire in the direction of the player's party. This is a Mars-based attack with a base power of 180 and a range of 3 targets (the characters to either side of the primary target will only take 50% of the attack's force, instead of the normal 80%, however). Pyrodras use this with a Mars Power rating of 85.
 * Rising Venom: Used 1 out of 8 times, this Monster Skill has the monster lob a small amount of glowing green poison at a single party member. This is a Mercury-based physical attack that deals approximately 30 points more damage than a normal physical attack would. There is also a chance that the target will be Poisoned. Pyrodras use this with a Mercury Power rating of 115.

Pyrodras tie with Puppet Warriors as the slowest monsters in the lower areas of Treasure Isle. The two are not interchangeable, however, as Puppet Warriors have the Power Crush skill, which might automatically lower the target's Hit Points to 1. While Power Crush may appear to make Puppet Warriors the more dangerous of the two, it's worth remembering that the skills available to Pyrodras make them more consistently powerful: Triple Chomp, as always, can cause a lot of damage individually; Rising Venom, while not as powerful, may Poison someone, which can be even more dangerous if left unchecked (although, at this point of the game, Poison is more of an annoyance than a proper threat).

Pyrodras are among the most contradictory monsters in the series: Even though its name and the Fire Breath skill suggest a more fire-oriented monster than the previous versions, Pyrodras are still water-based monsters at heart and fire is still its weakness. On the other hand, they are the primary source of Salamander Tails, a forgeable item that can be made into a variety of Mars-based equipment. Due to this item, Pyrodras will likely be "farmed" often, or become the targets of Random Number Generator manipulation for guaranteed item drops.

Hydra
A Hydra is a varant with brown scales and a green underbelly. In Golden Sun: Dark Dawn, they are fought in Barai Temple.

Hydras have access to the following battle commands:
 * Attack: Used 6 out of 8 times, this is the monster's standard physical attack.
 * Mesmerize: Used 1 out of 8 times, this is a Monster Skill that has the monster spews large mounds of light purple gunk on the player's party with the battle text reading "Hydra stares... Mesmerize!" This skill doesn't deal damage, but it has a range of 5 targets and may reduce the Defense rating of each affected character by 12.5%, down to a minimum of 50%. This appears to be the Slaver Monster Skill from the previous game, just renamed.
 * Triple Chomp: Used 1 out of 8 times, this is a Monster Skill where each of the monster's heads attacks a single party member. This is a that deals approximately 1.7 times as much damage as a normal physical attack would. Hydras use this with a Mercury Power rating of 115.

Once again, Hydras are slower than any other enemy in the region they inhabit. They are also among the least durable, although they make up for this with decent Attack. Ironically, they also give out the most experience points for that area, suggesting that their skills compensate for their lackluster statistics.

It is worth noting that Triple Chomp now deals less damage than it did in Golden Sun: The Lost Age (the damage multiplier is reduced from 2.4 to 1.7). This makes Hydras less dangerous than they used to be, although the skill is still fairly powerful.

Aqua Hydra
An Aqua Hydra is a varant with blue scales and a light blue underbelly. In Golden Sun: Dark Dawn, they are fought in the Belinsk Ruins.

Aqua Hydras have access to the following battle commands:
 * Attack: Used 4 out of 8 times, this is the monster's standard physical attack.
 * Mesmerize: Used 1 out of 8 times, this is a Monster Skill that has the monster spews large mounds of light purple gunk on the player's party with the battle text reading "Hydra stares... Mesmerize!" This skill doesn't deal damage, but it has a range of 5 targets and may reduce the Defense rating of each affected character by 12.5%, down to a minimum of 50%. This appears to be the Slaver Monster Skill from the previous game, just renamed.
 * Triple Chomp: Used 1 out of 8 times, this is a Monster Skill where each of the monster's heads attacks a single party member. This is a that deals approximately 1.7 times as much damage as a normal physical attack would. Aqua Hydras use this with a Mercury Power rating of 115.
 * Rising Venom: Used 1 out of 8 times, this Monster Skill has the monster lob a small amount of glowing green poison at a single party member. This is a Mercury-based physical attack that deals approximately 30 points more damage than a normal physical attack would. There is also a chance that the target will be Poisoned.
 * Drench: Used 1 out of 8 times, this is a Psynergy technique that drops moderately large spheres of water onto the opposition, dealing a Mercury-based attack with a power rating of 60 and a range of 3 targets. This ability consumes 10 of its user's Psynergy Points; an Aqua Hydra has enough PP for two castings.

Unsurprisingly, Aqua Hydras are much slower than any other enemies that may fight alongside them. They aren't the most durable enemies around, either, although they are among the strongest. Because of this, players should be ready to heal as soon as an Aqua Hydra uses Triple Chomp. Oddly enough, Aqua Hydras are the only monsters in Belinsk Ruins that are weak to fire; all the other enemies are vulnerable to wind.

Pyrodra
A Pyrodra is a varant with wine-colored scales and a bluish underbelly. In Golden Sun: Dark Dawn, they are fought in Burning Island Cave.

Pyrodras have access to the following battle commands:
 * Attack: Used 5 out of 8 times, this is the monster's standard physical attack.
 * Fire Breath: Used 1 out of 8 times, this Monster Skill has the monster generating a mass of fire in the direction of the player's party. This is a Mars-based attack with a base power of 90 and a range of 3 targets (the characters to either side of the primary target will only take 50% of the attack's force, instead of the normal 80%, however). Pyrodras use this with a Mars Power rating of 115.
 * Triple Chomp: Used 1 out of 8 times, this is a Monster Skill where each of the monster's heads attacks a single party member. This is a that deals approximately 1.7 times as much damage as a normal physical attack would. Pyrodras use this with a Mercury Power rating of 85.
 * Rising Venom: Used 1 out of 8 times, this Monster Skill has the monster lob a small mount of glowing green poison at a single party member. This is a Mercury-based physical attack that deals approximately 30 points more damage than a normal physical attack would. There is also a chance that the target will be Poisoned. Pyrodras use this with a Mercury Power rating of 85.

Pyrodras are generally inferior to Brutal Trolls, the only other type of monster found in the Burning Island Cave. In an interesting twist, Pyrodras are actually faster than Brutal Trolls, as opposed to other Hydra species which are typically the slowest enemies around. Pyrodras also give out more experience points than Brutal Trolls, suggesting that Pyrodras have more dangerous skills.

Their speed isn't the only thing that has changed: Pyrodras are now fire-based monsters, rather than water-based as they were in Golden Sun: The Lost Age. Their Power and Resistance ratings for both Mars and Mercury have been reversed, leaving them vulnerable to water attacks and strengthening their Fire Breath skill. On that note, much like Triple Chomp, Fire Breath has been weakened since The Lost Age (its base power is now 90, half of the 180 it used to be).

Cultural References
Origin: Greece

The Hydra (also known as the Lernaean Hydra) in Greek mythology was an ancient serpent-like water beast that had multiple heads and toxic breath. The Hydra of Lerna, which was slain by Hercules for his Twelve Labors, lived in the Spring of Amymone. Its blood was then used by Hercules to make poisoned arrows for future tasks.