Doom Dragon

The Doom Dragon is the final boss in Golden Sun: The Lost Age. While powerful and very durable, it is outdone by Dullahan in sheer ferocity.

As a boss
Doom Dragon is the only enemy to have three appearances in the same battle; it is essentially three enemies, fought one right after the other. The three forms taken together gives the Doom Dragon a grand total of 13,200 HP. It is very resistant to Venus and Mars attacks. Only its Jupiter resistance is average.

First stage (Three heads)
The first stage of the Doom Dragon battle features 5000 HP, and the dragon can act four times per turn. Most of its attacks are not so strong, though. Doom Dragon can defend, its Psynergy collection includes Earthquake, Quake Sphere, and Thorn for minor Venus damage, Flare Storm and Fiery Blast for Mars damage, Cure for itself and Haunt and Curse for the party, and its Monster Skills include Gravel Blow (Venus damage), Blast Breath (Mars Damage that also lowers defense), Earth Force (renders one character unable to move for a turn, but usually hits after the character has taken its turn, making it useless), Psy Boost (to recover PP), and Djinn Blast (to drain all Djinn of one party member, making that member very weak for at least several turns).

Second Stage (Two heads)
The second stage of the Doom Dragon battle features 4200 HP, and the dragon can act three times per turn. Many of its attack Psynergy is stronger than in the previous stage. Doom Dragon retains its Haunt, Curse, Blast Breath, Earth Force, and Djinn Blast skills, but its Psynergy collection is now comprised of Spire, Clay Spire, and Briar for Venus damage, Inferno and Serpent Fume for Mars damage, and it gains the Monster Skills Desert Gasp (Replacing Gravel Blow to do Venus damage alongside lowering the party’s defense), Guard Aura (to make Doom Dragon next to invulnerable for that turn), and the terrifyingly powerful and spectacular Cruel Ruin sequence that could be treated as a Summon sequence. Visually, Cruel Ruin resembles circular patterns in the sky above the landscape gather energy into one point and explode into an array of divine, winding beams of light that lay siege to forests, and one beam strikes the party and bathes them all in the glow of this destructive force. Obviously Doom Dragon is much more dangerous in the second stage; this is where summoning Coatlicue or Iris may prove life-saving.

Third Stage (One head)
The third stage of the Doom Dragon battle features 4000 HP, and the dragon can now only act two times times per turn, and the physical number of moves in the Doom Dragon’s inventory is now lower than before. In spite of this, the Doom Dragon becomes immensely more dangerous than even its second stage: It can use Earth Force, Guard Aura, and the extremely powerful Cruel Ruin as before, Stone Spire and Nettle for moderately strong Venus damage, the new Darksol Gasp which does strong Venus damage and may Haunt each Adept affected, and its most crippling, potentially game-ending talent of all: Djinn Storm, which completely drains all Djinn of all current battling Adepts like Djinn Blast, making all Adepts involved very weak for at least several turns each. If the Doom Dragon uses Cruel Ruin right after Djinn Storm, it is very likely that more than one of the current battling Adepts will be downed.

In the story
At the top of Mars Lighthouse, the Wise One appears before the party. He says that he has no power to stop them from firing the beacon, prompting him to ask what would happen if a miracle were to occur. He summons the Doom Dragon to face Felix and co. The party is determined to defeat it, and by the time Kraden connects the dots and discovers that the dragon actually is Isaac's father Kyle and Felix and Jenna's parents (much like Saturos and Menardi were the Fusion Dragon), it is too late.

After the the fight, Kyle and Jenna and Felix's parents are practically dead. When Mars lighthouse is lit, their parents are miraculously restored by the beacon's power. Afterwards, Kraden hypothesizes that the Wise One, who apparently knew that the parents would be revived by the beacon's light, forced Isaac and the others to fight and destroy their own parents to test whether or not the party would be able to use the power of Alchemy responsibly.