WotonWoton is chief of the gods and keeper of covenants and promises. He is married to Fricka, the goddess of house and home.
Woton hired two giants, Fasolt and Fafner, to build a gleaming fortress / palace called Valhalla. In exchange for their labor, he promised to give them his wifes sister, Freia. Unfortunately, this was a promise he never intended to keep. Fricka is understandably angry with her husband for giving away her sister. As the giants come to collect their fee, Woton commands Loge to find an acceptable payment in lieu of Freia. This results in Loge telling the two giants of Alberich and the Rheingold. The promise of power and the ability to escape from the deal with the giants interests the gods, including Woton himself. Thus begins the chain of events that eventually lead to the destruction of the entire world, including the gods.
It could arguably be said that it was Wotons greed for possessions [his home], and hypocrisy [intended not to keep a deal when he himself is supposed to act as enforcer of all contracts] is primarily responsible for the downfall of the gods. With his imprudent decision to wager the source of his (and the other gods) immortality for a palace (i.e., material goods), Woton was as guilty as Alberich for the destruction of the world.
FrickaAs mentioned previously, Fricka is the goddess of house and home and wife of Woton. She is also the sister of Freya. Fricka urges her husband, Woton, to obtain the ring after she learns that it could be used to keep him faithful. In Die Walküre, it is Fricka who tells Woton that he must defend Hundings marriage to Sieglinde against the Siegmund. Woton is reluctant because he believes that Siegmund could save the gods by restoring the Rheingold; however, if he refuses to defend Hunding, he will lose his power.
FreyaFreya provides the other gods with golden apples that ensure their eternal youth and power. Her abduction by Fafner and Fasolt after the completion of Valhalla is devastating to the gods, who begin to age immediately. Had Freyas presence not been absolutely essential to the survival of the gods, Woton and company may not have gone to the trouble to rescue her.
AlberichAlberich sets in motion the entire Ring by renouncing love and taking the Rhinegold from the Rhinemaidens. After his brother, Mime, fashions the gold into a ring of immense power, Alberich enslaves the other gnomes of the underworld (Nibelheim) and forces them to mine gold for his treasury.
Alberich obtains a magical helmet (the Tarnhelm) that allows the wearer to change shape and size. Loge and Woton descend into the underworld and trick Alberich into turning into a frog, after which they steal the helmet and force him to give up his wealth to Fasolt and Fafner. He curses the ring, saying all those who possess it will encounter envy and death until it returns to his hand.
In the opera, Alberich represents the archetype of power being evil and loveless. Some authors have interpreted his character as Wagners embodiment of the evil Jew*.
FasoltFasolt and his brother, Fafner, built Valhalla for Woton in exchange for Freya. When Woton attempted to back out of the deal, it was Fasolt who refused to allow it, due to his infatuation with the goddess of youth. It was also Fasolt that refused to accept Alberichs wealth in exchange for Freya unless it was enough to hide her from view. When Woton eventually gives up the ring to the giants (to fill the gap in the wall of gold that hides Freya), they begin to fight and Fafner kills Fasolt.
*Gottfrieds strine journey: A Wagner faces his ugly heritage, by Daniel Mandel. Published in the July 2000 edition of AIJAC the Australia / Israel & Jewish Affairs Council.