Cyrus's arcane focus is the devil ray tattoo on his back. When in use it glows a golden color. The ray is made up of waves with a sun symbol at the center. The three characters in the middle say sun in infernal.

He got it when he was younger and working on a transport ship. He met another tiefling who was a passanger on the vessel. The tiefling also taught him how to read and write in infernal.

The few months that the two were together on the ship made a very large impact on Cyrus. Without this experience I think Cyrus would have turned out a lot more bitter, cold hearted, and cruel than how he actually ended up.