Arcades and Dremoka

Karthus is from Alara, called the tyrant of John. Johnny encountered him on his very first planeswalk. Nickel bolus captured Karthus along with four other smaller dragons and brainwashed them into serving Sarcan. Arcades was the first of the elders to name himself. He lost interest in investigating human structures while the other elder dragons were still being born. Dremoka has a love for buildings because he's like an architect.