One lesson I learned the hard way - avoid making cards that are balanced only due to the existence of PC. I am unsure of whether a sanc deck runs PC 100% of the time , which means there is a good chance the "death knell" Oldtrees described would happen.
The ability is rather strong and perhaps a bit too hard to counter. The RNG is known to bottomdeck multiple key cards (including all your pillars sometimes), and if all the Jesters are bottomdecked except for one (the one you play), it would probably annoy the opponent a lot unless you decide to swap decks back - highly unlikely as you've probably planned for this (terrible RNG or not) and have Sanctuaries to prevent a reswap and Mindgate to continue using your deck. Another worry I have is that you could create a "Kamikaze" deck using this - make a deck with pillars of your mark.... and cards that aren't the same element as the pillars or your mark. Play Jester, and swap to leave your opponent with a dead deck, again causing frustration.
The card might be balanced, but it's the power of the ability that worries me.
Seasonal Rare is an interesting possibility that could see future Card Design use though.
Just my 2
on the card.
