Plainswalker availability?

senectus

I started this game a while back when it first came out in beta. then came back again recently.
What I've noticed in the forums is people talking about plainswalkers that i dont see as being available.

Whats the go with this?

Do they become on sale randomly? do their availability ebb and wane due to some schedule or just randomly? 

rafalele

There is an schedule but it is not public, do not know why.

It rotates the plainswalkers avaible every thursday. 

Here you have the only official information about this theme : https://d3go.helpshift.com/a/magic-puzzle-quest/?s=gameplay-questions---planeswalkers&f=which-planeswalkers-are-currently-available-in-the-vault