Exodus of the Neutral Dragons

Immediately after the Chromatic Dragons stopped the forge gods from turning all chromatic dragons metallic, a war ensued between chromatic and metallic dragons. A group of dragons of both types, tired of the fighting, performed a ritual to take them somewhere where they could live in peace. They were never heard from again.
Unbeknownst to anyone in their original homeland, these dragons found the haven they were seeking - their ritual transported them to the Psionic Realms, crashing into the Living Gate and destroying it, with no way to contact or return to the Arcane Realms. They settled in, adapted to their new home, and became gem dragons.