Protection from "creature"
I've been playing "Jumpstart: Historic Horizons" recently and, twice now, I've had different opponents select "Creature" for "card type" when deploying "Serra's Emissary". I had no idea that this was a valid card type. I was thinking the intent behind the ability was something more along the lines of "protection from goblins" or even "protection from <color>". However, if "Creature" is valid (and, clearly, it currently is), it seems ridiculously over-powered. It effectively means that the game has immediately ended because all of my creatures, no matter how powerful, will be unable to damage either my opponent or any of my opponent's creatures. The only way out of this situation would be to have an exile or damage spell capable of taking "Serra's Emissary" out, which would be very difficult as is since "Serra's Emissary" is a 7/7 creature. Further, since "Serra's Emissary" is not legendary, additional "Serra's Emissary" cards could be deployed to provide protection from "instant" or "sorcery" rendering the opponent completely immune.
I'm sure this is fun for someone deploying "Serra's Emissary" but it certainly isn't fun for me as a recipient of the effect because there is nothing more I can do.
Is this effect intended or is this an oversight?