I take those information by a book that i studied in high school...i hope the traslation is right! If you want other information for particualry gods or greek name, tell it to me, I'll find them surely...Lethean river
= Is in the Greek Hereafter, the "River of Oblivion", which waters, drunk from the souls bounded to reincarnate in new boidie, erases the remembrance of their past life. In OLYMPUS, lethean goddes, the "oblivion", the " forgetfulness", is the daughter of ERIS, the Discord. Some sources attribute to her (lethean) the motherhood of CARITI (Gracies in latin), the sons of ZEUS, and probbaly also of DYONISIUM, probably because he is the god of vine, which fruits give the oblivion.Stygian River
= According to some sources she is the oldier of the nymphes of the Oceans, for others, she is the daughter of EREBO (the male principle of primitive darkness) and NUX (the Night). She is an infernal goddes, a solitary inhabitant of TARTAR. From the rocks of her residence flows the poisonous water called "Stygian river", that other gods use for solemn oaths. It represents the Underworld and the Hereafter. Its name means "Hateful", "Horrid". Aphelion
= is right the explanation of Emperor Konny, but the right origin si "APO"+"HELIOS" (apo= nearer to, closer to, helios= the sun).