A few questions about Eternal Lake

I was taking a look at the forum and I saw the Eternal Lake
In the description it says that you can be there only if the guardian finds you worthy
So here are my question:
1 Who is the guardian?
2 What do you have to do in order to be found worthy?
3 If it is not a dungeon,how can you meet pokemon there?

1) Mew
2 and 3) It is a plot based area, one that will likely be explored in Guild explorations to come. The entirety of the Sacred Lands(the forum area in which the lake lies) are locked to all but Guild members who have reached a certain rank, meaning that not just anyone can go there and hang out in the first place.