The key which opes the well-like orifice / That leads to the Ploutonian abyss / Was given him, and when he opened it / Dense smoke ascended from the dreadful pit, / As from a mighty furnace, and the sun / Through smoke-beclouded air showed dim and dun; […]
Source: wiktionary
Although The Demeter births the Ploutonian figure that initiates Lucy’s ordeal, it will be Jesus Christ that resolves her wayward vagabonding.
Source: wiktionary
At Eleusis, there were three places recognized as entrances to the Underworld. There is the Ploutonian Cave, which you encountered earlier. The Kallichoron Well, the Well of Beautiful Dances, was supposed to be an entrance to Hades and is really close to the Ploutonian Cave.
Source: wiktionary