This is the Veritas. The gift of my first ancestor to our bloodline. Only a few times in the history of Prythian have we used it—have we unleashed its truth upon the world.Morrigan
The Veritas is a magical orb that contains truth magic.
The Veritas is contained inside a black box. It is a silver orb, no larger than a ripe apple, easily fitting in the palm of Morrigan's hand.
When it was used to prove Velaris existed, a pale cloud swirled inside then more clouds appeared to leak from the orb. An illusion appeared, showing the city from Rhysand's eyes. Once done, the illusion faded, color and light sucked back into the orb.
The Veritas has belonged to Mor's family for a millennia. It is one of the family's most valued and guarded talismans.
Rhysand, Feyre Archeron, Mor, Cassian, and Azriel visit the Court of Nightmares with the intention of stealing Keir's orb to give to the Mortal Queens proof that Rhysand wants a better world for mortals and faeries alike. They are going to show them the truth of Velaris, the Court of Dreams, but since he knows that the queens will not want to enter Fae territory, they have to show them through an object that guarantees the truth of his words. When they are in court, Rhys keeps Keir entertained by asking him for unnecessary information while Azriel steals the orb.
They then used the orb to show the truth to the queens as the orb had been used in the war, it was known to humans and, by extension, the Mortal Queens, but they still don't want to give up their half of the Book of Breathings. Since they no longer have a use for the orb, they return it to Keir without him knowing it was ever gone.
Somehow Rhys gives Mor the orb so she can share with Nesta Archeron her memories of the waltz dances of the Hewn City, the Autumn Court and Fae in general, and the music that accompanies them as she has to prepare to dance with Eris Vanserra in the Winter Solstice ball held at the Court of Nightmares.