Doom Dragon

The Doom Dragon is the final boss in The Lost Age.

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.

First stage (Three heads)
The Doom Dragon acts four times per turn, but its attacks are comparatively weak.

Second Stage
The Doom Dragon acts three times per turn, but it gains the immensely powerful Cruel Ruin attack. Visually, a large circle appears in the sky, and it seems to then explode, releasing a large number of rays of light. One lands on the entire party, causing upwards of 200 damage. It helps to summon Coatlicue to heal the party after the Doom Dragon uses this attack.

Third Stage
The Doom Dragon acts two times per turn, but it gains the crippling, potentially game-ending Djinn Storm move.

In the story

 * WARNING: ENDING SPOILERS AHEAD

The Doom Dragon turns out to be Isaac's father Kyle and Felix and Jenna's parents. Both are practically dead.