Mutant creeper/mutant zombie mod? or maybe, (have no idea what version) tale of kingdoms, which I'm not sure is compatible. Even if you want to make it a zombie exclusive mod, just maybe DayM mod. I play with that on another modpack, thought it was pretty cool. What about a texturepack built in, such as sphax or dokucraft. Either or, I'm not sure. Shaders mod, even though it's massive, it's pretty cool, but I'm not sure what version it is.
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