Seems like it needs more defense and if your going to go to all the trouble of killing the Malignant cells perhaps a Bonewall would see a better bonus to the deaths. Also It would be hard but Unstable Gas would be (in my opinion) better because it isn't as random as Pandemonium. I haven't used Pandemonium much though so it still could work your way. An interesting description but Skeletons don't seem like a strong game winner. Also, if you do add Unstable Gasses then you can also add Explosions and have your mark Fire to get rid of the blocking shields and make your Skeletons more useful.