The door will not open via the Open menu option, nor by double-clicking or using the F key. You must right-click and select Use.
HailThe Maelstrom. If the event is ready he will ask you if you are prepared to face the storm. If you say yes, this will trigger 3 waves of elementals, followed by Magnimaclus. If the event is not up, The Maelstrom will say "the storm has subsided."