The Radiation Gate is located in Auldrant's south pole, and it serves as the exit point for memory particles of the Seventh Fonon. The gate is located in a deep, rugged chasm containing several fossilized bones of monsters. At the bottom of the gate is the passage ring for the first Sephiroth Tree and fonic glyph that keeps the gate operational.
The Radiation Gate was built during the Dawn Age. During the events of the story, the protagonists originally intend to journey to the gate to control the Sephiroth Tree for the safe descent of the Outer Lands. However, due to Van Grants's actions at the Absorption Gate, Jade Curtiss states there is not enough time to do so as the pary finishes connecting Mt. Roneal's Sephiroth. To compensate, Asch travels to the Radiation Gate so that he and Luke fon Fabre may control both passage rings at once. The party first visits the Radiation Gate in a attempt to deactivate Eldrant's barrier. Due to Noelle's piloting skills, they manage to escape the fonon barrage and safely land inside the gate. At the bottom, they confront Grand Maestro Mohs, who is on the brink of losing his sanity due to the rejection of Seventh Fonons in his body. They successfully defeat him and deactivate the fonic glyph operating the gate. With the deactivation of both gates, the party prepares for the infiltration of Eldrant.