I should be able to afford a monthly subscription in a couple of months but can't find any information about the "Special Opponent - A battle opponent that only subscribers can face." Is this a one off battle opponent or do we get a new one every month?

we get one extra battle opponent in the “cash shop” section of challengers that does not change - the bewitched bookcase challenger. c:

https://subeta.net/petinfo.php?petid=940284#/BattleGuide/BewitchedBookcase">here is ’s data on the challenger!

Thanks