This is because the name is Chthonia not Achthonian. Achthonian is masculine gender and second the first "A" implies negation, as in "not of the earth".
So google Chthinia, and here is some info to get you started from http://www.mythindex.com/greek-mythology/C/Chthonia.html
The mention of her name is seen in Erechtheus, a lost play written by Euripides. Euripides gave the king three daughters, one of whom was appropriately named Chthonia. At war with neighbouring Eleusis and its ally King Eumolpus, Erechtheus learned from the god Apollo that Athens would win if he sacrificed his daughter. He sacrificed Chthonia, and her sisters insisted on sharing her fate. Erechtheus won the battle, but, in the moment of victory, he was destroyed by Poseidon or by a thunderbolt from Zeus. In early times, death by thunderbolt was believed to be a prelude to a privileged afterlife.
Subject: Godess that is recorded but has no information on anywhere 
Tue Oct 06, 2009 5:40 pm
