Just finished the campaign and was a bit confused by the status of Caylen and the gate just before the final events. I thought the gate was closed thousands of years ago by the Cerim (who subsequently disappeared), so I was pretty confused when Seline spoke about growing up there.
Reading around and watching YouTube it seems the gate was created a thousand years ago by the Cerim but closed a year before the start of the game. Might be good to make this clearer before the above events.