I think this type of planet would not only be extremely fun but scary too. This planet could be added into the story as well! The infected planet idea kind of (and by kind of, I mean it is) inspired by Dead Space. This planet would involve not only humans(Or any other race) but NPCs and hostile enemies. Upon arriving NPCs and Enemies will be extremely hostile attacking on sight. The NPCs and enemies will have a specific tint (Maybe green maybe red, ehh) or a noticeable trait such as tentacles in the back of their heads or spines. (Much like the depictions on the Ark! You know the tentacle monster) The infected could burrow out of the ground and chase you restlessly adding much stress and difficulty when playing on this high tier planet. The planet could also provide some residue evidence under ground such as strange Ark like portals or laboratories. (The origin of the parasite would be left to the developers) The enemies will also have a chance of spawning a parasite on their bodies upon death. The parasite would be mostly harmless but if it latches on to you (Not like a face hugger, although possible I'm thinking like a latch on your body) it will cause a strong and lengthy poison effect or an effect that works somewhat like the confusion in terraria where your character does things you don't want it to do. All life won't be infected on this planet however, although plants are trees and water will, there would be underground bunkers with a resistance team offering quests such as eliminate --- zombies or place a satellite or a comms station and they would offer vanity items, swords and guns and pixels as well. There will also be bandits and cultists that will be more dangerous than the rest (the cultists spawning parasites from underground and etc.) While the bandits travel in large groups. Both of these can drop mob specific items such as a cultists ritual dagger that has a parasite effect on other worlds. There would also be a final boss to this planet. (Keep in mind, this planet is more fighting and exploration than mining) After doing several missions for the resistance(The resistance could be a team of survivors like the survival outpost or a heavily government program) you would then be prompted with a mission that could find the source. The source could be heavy amounts of parasites underground(You needing to kill hundreds) and then you would be able to get an item that summons a boss. The boss would be a large parasite-like creature with tentacles (similar to the one on the ark, but not quite) and it would shoot you with parasites, spit and during this fight many hostile enemies (not just parasites) will spawn from the ground. The parasite would also be flying above you(although not too high) and chasing you even if you go underground. The rewards for killing this boss could be a resistance mech, a nifty gun that shoots parasites, or a staff of infection that summons friendly infected from the ground and attacks enemies. (Epic late game drops!) So guys, tell me do you like it, hate it, love it, or think it could use a few things as well?