The Dragon Below

The Knowledge Religion check is good, altho the 18 is the same as a 10 (untrained you can't roll higher than a 10 on any Knowledge check), but 10 was the DC.

The symbol that Merrick sketched looks like this.

The Dragon Below is a scattered group of cults in Khorvaire, mostly they are disorganized and plan some evil. The ancient myths of Eberron have the world formed by three fighting dragons, one of whom was Khyber. Khyber lives 'below' and is considered to be locked into the world. The Underdark of Eberron is called Khyber. Cults who worship the Dragon Below range from orgaqnized and sisister crime/religious cabals to nitwit wanna-be goth kids rebelling as can be found here.

So who knows what it means...