|“||I'am going to find this Isaac... And I swear that the last thing he sees will be Karst avenging the death of her dear sister!||„|
|“||Your hand... so warm... People have such warm hands... I had forgotten...||„|
|~ Karst's last words to Felix|
Karst hails from the northernmost settlement on the world map, the town of Prox, and lived with her sister Menardi; though they are sisters, they look nothing alike. Karst and the other people of Prox are of a human-like race that is distinctively characterized by almost reptilian scales and spikes on various areas of their flesh - but more importantly, their natural proficiency to the Mars element. They are thus afforded both a natural toughness and a natural immunity to the constant cold of their environment. While Karst appears to be a powerful warrior in her own right, Agatio appears to have the higher authority of the two because his strength and power is claimed to approach that of Saturos.
At the start of the first Golden Sun, she and Agatio remain in Prox as Menardi and Saturos and their recently discovered companions Alex and Felix depart from Prox to set out on their quest to restore the force of Alchemy to the world, thereby stopping the continued growth of the abyss at the end of the world that threatens to consume Prox in the future.Felix's parents and Kyle, whom Saturos and Menardi rescued from death previously, also remain behind at Prox, and are essentially kept incarcerated there on Saturos' order so that Felix is coerced into willingly assisting Saturos on his quest; only once the four Lighthouses are lit, subsequently restoring Alchemy to the world, will the parents be freed.
After the battle, Karst and Agatio was turned back to normal. They found out that they were dying, due to their loss of energy during the battle. When they see that Felix is in their precense, they begs him to take the Mars Star and light the beacon. After Felix lights the beacon (after a battle with the Doom Dragon), they both die of fatigue. It's unknown if Karst forgives Isaac for her sister's death, but one theory is that she did forgave him.