The Ultima Gate (アルティマゲート, Arutima Gēto?) is a portal central to the plot of World of Final Fantasy. It links Nine Wood Hills to other realms and can only be used by Mirage Keepers like Lann and Reynn.
Hoping to improve their mother's way of life, Lann and Reynn approach the Ultima Gate to bring a god into Nine Wood Hills. The twins successfully summon Brandelis, but the malevolent Exnine Knight captures their parents and allows two of his allies, Segwarides and Pellinore, to possess their bodies. Having doomed their world and all those to which it is connected, Lann and Reynn flee in terror.
One century later, Enna Kros calls Lann and Reynn to Grymoire so they can make amends for their mistake. The siblings, who do not remember their past, are unwittingly manipulated by Brandelis and his henchmen into ascending a Crystal Tower, atop which the Ultima Gate is located. A masked woman convinces Lann and Reynn it is the key to reuniting with their missing mother, and the twins open it. Swarms of Cogna begin to invade, and Brandelis, Segwarides, and Pellinore emerge to celebrate their victory. Grymoire is slowly corrupted, and as chaos spreads, Lann and Reynn travel to Brandelis's stronghold in hopes of vanquishing him for good and undoing the damage they have caused. They fail to do so.
In an alternate timeline, Lann and Reynn use the Ultima Gate to force the Cogna out of Grymoire. Once the twins defeat and subdue Brandelis, they allow themselves to be sucked into the portal, as well. This causes the Ultima Gate to vanish.
Ultima means "the last" in Latin and many Latin-based languages. In the Spanish versions of many Final Fantasy games, the spell Ultima's name is written as "Artema", a close transliteration of the Japanese katakana.