Hey! Parasitic Mage/Sorcerer (Can't remember right now), doesn't work like the other cards. When discarded it only adds to the hand once and will never retrigger. Also parasitic duplicates don't work for each just the first one activated, not sure if that's intentional or not.
Also, I realy enjoy the battle scaling! It's a little buggy sometimes but it's a nice addition!
Yeah, I noticed this when trying to build a Parasitic Magus + Parasitic Succubus deck. In my experience, the first copy of a Parasite you discard will spawn a second copy to your hand, but you can't get any additional copies of that particular Parasite until you play one, but you CAN get more copies if you later discard it again after playing one. (Except for Parasitic Magus, haha)