Poseidon (ポセイドン, Poseidon) is a mythical figure in Weyard’s past and serves as a boss in Golden Sun: The Lost Age. Among boss monsters he serves a notable influence upon plot progression. He resembles the classic image of king Triton.
 As a boss
Poseidon blocks the way into Lemuria and ensures that you cannot enter the place until you’ve thoroughly explored and completed the entire Great Eastern Sea. Otherwise, you’d be able to enter Lemuria as soon as you first acquire the Lemurian Ship. Poseidon achieves this not because of being too tough a boss; it’s that in battle, no attack whatsoever can damage him because of an impenetrable force field that guards him. Only using the completed Trident of Ankohl as an item can remove the force field of Poseidon, after which it becomes a normal boss battle that can be completed. The Trident can only be completed through thorough journeying and event completion around the Great Eastern Sea. (On a related note, Poseidon can be encountered in the Monster Battle mode, but fortunately he does not possess this invincibility.)
With the Trident in tow, Poseidon becomes a normal boss, and he has the following statistics: 4905 HP, 162 PP, 302 Attack, 100 Defense, 185 Agility, 47 Luck, and he can act twice per turn. In terms of resistance, he has a Mercury resistance rating of 175, a Venus and Jupiter resistance rating of 100 each, and a Mars resistance rating of 25, and in regards to his abilities he uses his available Mercury-based attacks with a Mercury power rating of 115. When he is felled, the party nets 2930 Experience and 3762 Coins and is guaranteed to receive a Psy Crystal.
Poseidon employs 2 in the following list of battle commands each turn:
- Attack: This is this monster's standard physical attack, which is closely connected to the enemy ability detailed below:
- Counter-rush: A unique enemy ability that always acts first if Poseidon decides to use it in a given turn. A brief blue watery effect ensues at Poseidon's position (resembling the swirling water effect that occurs at the point of impact during the Froth Spiral Psynergy). For the rest of the turn, any time an attack attempt or Psynergy attempt is made on Poseidon by an Adept (can be anything: an Unleash, a debuff like Impair, a miss, a Summon...), Poseidon automatically attacks the Adept in question with a standard physical attack. All of this works whether Poseidon's force field is up or down. This goes a long way to making Poseidon the dangerous boss he is, since on a turn where one of his battle commands is Counter-rush, if all four Adepts attack or do anything else to him, all four of them will end up whacked physically, and that's in addition to whatever is his "normal second move" he would perform that turn. On a side-note, in battle mode, if the player uses Mold on him while he uses counter-rush, he will take damage, then attack himself due to Mold's effect.
- Deluge: This is a Psynergy spell that rains down an array of watery spheres on the party, dealing a Mercury-based attack with a power rating of 120 and a range of 5. This ability consumes 20 of its user's PP.
- Ice Missile: This is a Psynergy spell that shoots a prolonged mass of spiked ice into the positions of the Adepts, dealing a Mercury-based attack with a power rating of 160 and a range of 3. This ability consumes 23 of its user's PP.
- Ocean Fist: This is a monster skill where Poseidon engulfs and launches a targeted Adept within a colossal, screen-filling, bluish-white tornado-like spout of water (large enough to give the impression that it has to affect the entire party), either dealing a non-elemental attack (ironically NOT Mercury-based) equal to its normal physical attack with an additional 50 damage points or reducing the Adept's HP meter down to 1.
- Ply Well: This is a Psynergy spell that restores Poseidon's own HP by roughly 200.
- Typhoon Blow: This is a monster skill where Poseidon raises his trident to project an array of watery spheres at the Adepts, dealing a Mercury-based attack with a power rating of 150 and a range of 3 (the Adepts on either side of the targeted Adept will only take 50% of the attack's force, instead of the normal 80%, however).
- Watery Grave: This is a monster skill where the camera swivels to behind Poseidon as he summons a large wave presented as a 3D-effect to wash over the opposing party, dealing a non-elemental attack (ironically NOT Mercury-based) with a power rating of 130 and a range of All. In addition there is a good chance that each affected Adept will be instantly downed.
Jenna learns Serpent Fume at level 26, so training the party to that level may make this battle easier. Also, if all six possible Venus Djinn have been obtained at this point in the story, Felix can use the immensely powerful Odyssey in battle, the only disadvantage being that it doesn't capitalize on Poseidon's weakness to Mars-based attacks. Other ways to take advantage of this weakness would be to utilize the Pierrot's Juggle (Mars-based) abilities, or redistributing one or two Mars Djinn to each character, which may permit some unique strategies. By this point in the game, the player can have the first twenty-four Djinn available, six of each element, meaning a variety of options are available. Most efficient may be to put one Djinn of each element On Standby, allowing for two Barbarians and two Savants - have the Brutes spam Planet Diver against Poseidon, while the Savants heal using Wish Well as necessary or attack with Plasma or their physical attacks. Another option is to use four tri-elemental classes, which allows for a more diverse strategy. Ultimately, victory in this fight is a matter of patience and care - make sure nobody's HP goes too low, and Poseidon will go down eventually.
 Background and Story
Poseidon is an entity that has long slumbered within the depths of the Sea of Time, near Lemuria. According to NPCs in The Lost Age, Poseidon was once the "true rightful king of the seas" far in the past (perhaps Weyard's ancient past), and is apparently the "Sea God" that the Shrine of the Sea God in Indra is dedicated to. Further details to Poseidon's apparently important role in Weyard's ancient history are not provided. By the present age he has become a mindless monster that would cause terror if he wakes up.
At the end of Golden Sun and the beginning of The Lost Age, Mercury Lighthouse and Venus Lighthouse have been lit. This is what causes Poseidon to awake, and he in turn generates the large tidal wave at the start of the second game, the one that indirectly drives Piers out of Lemuria. As The Lost Age progresses, Poseidon is the reason why Felix and Piers are not able to enter Lemuria until much later in their journey across Weyard, when they have achieved the reconstruction of the legendary weapon, the Trident of Ankohl, needed to do combat with Poseidon properly.
Poseidon is eventually defeated by Felix's party when they attempt to sail into Lemuria, with the Trident of Ankohl in tow. Using the weapon, they break apart Poseidon's aura of invulnerability, and proceed to engage in a fierce battle until Poseidon is destroyed.
The the battle against Poseidon would become well-known in the 30 years following the Golden Sun event. By the time of Dark Dawn, a wooden replica of Poseidon appears as a obstacle in the Psynergy Training Grounds, a theme park representative of the exploits of the Adepts, now referred to as the Warriors of Vale. The replica consists of three wooden panels, showing Poseidon's head and fists, and each must be burned using Fireball to continue. However, "Poseidon" is blocked by three geysers of water, representative of the force field. To remove the force field Matthew and his party complete a series of three puzzles, which represent the three pieces of the trident. Once completed, the geysers disappear, allowing Matthew and his party to continue on.
 Cultural Allusions
In Greek mythology, Poseidon was the King of the Sea and one of the original 6 gods and goddesses in the Greek Pantheon. He was commonly depicted as carrying a trident, which the game provides a sense of irony for, as the tool that ultimately leads to his downfall is the trident. Poseidon was the brother of Zeus and Hades in Greek mythology. Poseidon was referred to as Neptune in Roman mythology. Interestingly, Poseidon appeared as a boss in Golden Sun: The Lost Age whereas his Roman counterpart (Neptune) appeared as a summon in both games and could even be used against Poseidon.
|Bosses in Golden Sun|
|Vault Bandits • Tret • Saturos • Killer Ape • Hydros Statue • Manticore • Kraken • Azart • Satrage • Navampa • Toadonpa • Storm Lizard • Tempest Lizard • Saturos and Menardi • Final boss • Deadbeard|
|Bosses in Golden Sun: The Lost Age|
|Chestbeaters • King Scorpion • Briggs and Sea Fighters • Aqua Hydra • Serpent • Avimander • Poseidon • Moapa and Knights • Karst and Agatio • Flame Dragons • Final boss • Valukar • Sentinel • Star Magician • Dullahan|
|Bosses in Golden Sun: Dark Dawn|
|Tangle Bloom • Dim Dragon • Dim Dragon Plus • Stealthy Scouts • Sand Prince • Ku-Tsung and Ku-Embra • Ice Queen • Sludge • Mountain Roc • Blados and Chalis • Blados, Chaos Hound, and Chalis • Final boss • Ogre Titans • Ancient Devil • Star Magician • Dullahan|