Interesting concept. I suppose the advantage of this over plague is that it would more likely kill the creatures it targets (faster), however it would miss out on affecting all of the target creatures (and removing invisibility?). Despite the fact that the targets will be killed pretty quickly in comparison to plague, the advantage of this should be that you affect the creatures they have that are central to their strategy, and all your counters will be useful (essentially more directed at decks without mass creature generation such as growth decks or skill creature decks). However I see two problems with this.
1) All the creatures around the Plague Bearer will probably only be fully useful (if you want to keep this concept) if they have mass creature spawning. In this case plague (or more than one) would be more effective since it targets every single one.
2) Spawns in a random empty slot. I suppose it would be included in the design that it wouldn't just spawn in the far right corner and stay lonely for the rest of the game, but you can't help but feel that there will still be a lot of luck involved in the location. If you could pick it yourself, then that is a completely new game changing mechanic already (as well as adding to the spawning on the opponents side)
I feel that with some revision to make sure that it is better than plague in some situations (roughly 50%- slightly less would be best if you were to go over or under) this card could be really cool.
