The Grimoire

Information
Not much is known of the Grimoire. Its origin remains shrouded in mystery.

What is known that, for centuries, only evil could handle it, due to a spell the Triad placed on the Grimoire, on the orders of the Source.

Whenever a new Source was crowned, the Grimoire was used in the ceremony, although exactly what role it actually played is also a mystery.

The Grimoire could also be used to bring a Demon back from the Demonic Wasteland

The Charmed Ones and the Grimoire
In 2002, Cole Turner became possessed by the Source. In time, due to the manipulation of the original Seer, Phoebe Halliwell became Queen of the Underworld. Since Phoebe was now evil, she could handle the Grimoire. Thus Cole and Phoebe began their brief reign as King and Queen of the Underworld.

However, Phoebe could not remain evil, the good in her won out. She, along with her sisters, Piper and Paige Matthews, vanquished Cole. Soon after, they managed to vanquish the entire leadership of the Underworld, including the original Seer.

Following that battle, the Grimoire was hidden in the Andes Mountains by Leo Wyatt.

Soon after, Cole, who had ended up in the Demonic Wasteland, following his vanquish, asked Phoebe to use the Grimoire to rescue him, but she refused. Cole, however, would soon manage to engineer his own escape.

Evil spell is neutralized
Following the destruction of the Triad in 2006, the spell that only allowed evil to handle the Grimoire was neutralized, although no one was aware of this fact at that time.

Rex recovers the Grimoire
In 2008, Rex Buckland and Hannah Webster returned to Earth and settled in Palo Alto, following the end of the Warlock Insurgency. Rex had begun to collect ancient books and scrolls, which he needed to help himself and Hannah gain vital information when needed.

Rex also felt that all knowledge, including knowledge found in these books, needed to be preserved. It was for this reason that, once Rex learned of the location of the Grimoire, he retrieved it and added it to his collection. Rex had already deduced that the Grimoire was now safe for good magic to handle.

The Grimoire is used to liberate Kira
It was around that time that the Charmed Ones discovered that Rex and Hannah were back in town and confronted them. The two former Warlocks related their story to the Halliwell sisters about their leading the Warlock Insurgency against the Source and how they'd turned their backs on evil.

As proof, Rex revealed his collection of ancient books and scrolls, including the Grimoire. Rex explained that the spell that only allowed evil to handle the Grimoire was no longer in effect and that it was quite safe for anyone to handle.

It was then that Phoebe Halliwell hit on the idea of using the Grimoire to rescue Kira the Seer from the Demonic Wasteland, where the Demon Zankou had vanquished her, four years before. With Rex’s help, the spell was cast and Kira was indeed liberated from the Wasteland and reunited with her human friends.

Future
The Grimoire remains in the possession of Rex and Hannah.

Whether or not they will use it again remains to be seen.

Other Copies
While Rex and Hannah retain their copy of the Grimoire, it has since been revealed that other copies exist. For example, this one.