In the Lion Arch Battle with where the new Red, Blue, Green knights. The portals they leave all seem to say that you need a “prime attunement” to enter.
One person said that standing on the coloured fields is the key.. but the conditions they leave lasts for 6mins. Each battle takes up to 40mins and 5mins to travel to each.
So far no one has yet to get a prime attunement.. let alone knows the exact way of getting one.
Though i think it’s ridiculous that we need something that is very hard to get to enter the portals, after all the previous battling we did.