Dlth'cho is the daughter companion in a binary star configuration. It revolves around its mother star, Yo'n'ia, in a tight and rapid orbit. It is a hot A-type star, but it is still significantly more luminescent than its Class-G mother. The most prominent metal burned in this star is hydrogen. Sunspot and solar prominence activity on the surface of Dlth'cho is heavily affected by Yo'n'ia. Gravitational eddies between the two stars pull on them, causing a unique system of solar "tides" that can be visually represented with special sensor equipment.

The Yo'n'ia system is compiresd mostly of small asteroids which may be the remnants of one or more ancient planets. The asteroid field begins some distance beyond the only planet of the system -- Tholia -- and continues to the edge of the gravitational hold of Dlth'cho and Yo'n'ia. Tholia holds the innermost orbit, which is tilted twenty-three degrees away from the solar plane. The bright stones and ores in the asteroid field glitter, giving Tholia a backdrop not unlike some artist's conception of a cosmic sea.

The Yo'n'ia system was the home of the Tholian Hegemony. Recently, the Tholians abandoned this system and all of their artificial structures. Their disappearance has left behind countless mysteries for the researchers of various governments. Why did they leave? Where did they go? The answers to these questions may be found in this system, a place as unique as its former inhabitants.