I only activated it once myself, but seen the zone wide message many times in the ToT era.
There is some timer on it, like once every 18 hours or 24 hours? it has a chance to spawn for like an hour or so, I remember people keeping timer and when time came everybody was going in to Thalumbra and mass-slaughering everything.
Everybody in zone will see the message about flurry or feathers and portal appearing but only 1 person who triggered it will actually see the portal.
There is a youtube video or 2 for the duck zone, it's groups of heroic ducks, level 100 iirc (whatever was max for ToT) and a final boss who drops a hat you can wear, so if you want different hats you're gonna have to try different arch classes
DO NOT leave the zone once you enter, you cannot get back.