Creatures existed before the creation of Eve's dream is regarded as [Ancient]. The most power powerful [Ancient] creatures are the [Elemental Beast]. They resided in orbs containing Eve's secondary power. It's said that look over humanity and is its guardians. They are Azure Dragon, Vermillion Bird, White Tiger, and Black Turtle.

The guardians have entered contracts with countless contractors but they have never give their [Authority] to any of the contracted contractors. It's said that it's impossible to gain their respect. 

In fact, they have already given their [Authority] to Eve. 

The [Elemental Beasts] were not created by Eve, unlike the [Celestial Wolf] and [Celestial Fox] but by the [Gods] instead. At that time, the [Gods] were in possession of their [Authorities]. They ordered the beasts to entertain as well as keep an eye on Eve. At first, they didn't like her because of the rumors they have heard, but through time they grew to love her. When Eve was sealed, they volunteered to guarded her secondary power, the [Elements] that was contained within orbs. At this point, they didn't want to be used by the gods anymore, so taking advantage of the gods being weakened after sealing Eve, they gave her their [Authorities]. These [Authorities] was divided equally between the souls. 

In summary, Eve's [Authorities] are the authorities of the [4 Elemental Beasts]. The Azure Dragon and Vermillion Bird's [Authority] went to Evangeline while the White Tiger and Black Turtle's went to Serena. These authorities were located and stored in the divided soul's eyes. 

However, Serena's left eye which stored the Black Turtle's [Authority] was gouged out so she's only in possession of The White Tiger's [Authority]