Gorgon in NA?

To my knowledge, she becomes available after completing Babylonia, and she's story locked which means outside of rate-ups, she can only be rolled on story summon.

She story lock servant. Got a pickup banner Babylon 2. So estimated time is End of November or Early December

"This Servant is LOCKED Locked until you complete Babylonia and will be added to the summoning pool once the quests are completed."

And bewared that she won't be rate-up in the first chapter release companion. But in the second summoning campaign she and Quetzalcoatl will be rated-up no matter you complete Babylonia chapter or not. After you complete that chapter she will be in story summon same as many SR.