I'm wondering too, cause I have no access to the new multiplayer mode or new Morty Deck. I have almost lvl 100 Mortys that I don't want to lose.
I am ShadowKyogre in Pocket Mortys Multiplayer. I experience bad lag at times, so if you're a friend trying to battle and it declines, it is the lag, not me. I'm up for a friendly brawl when I'm not hunting.