what you guys ran across was a Fort of Fortune, a world event that spawns naturally on skeleton forts and houses the much sought after "Chest of Fortune", to complete it you have to defeat an ashen lord in the fort itself along with a couple waves of skeletons
Super strenght >>>> invisibility, not just because of the no clothes argument.. we can only see because light enters our eyes.. if our eyes are invicible no light can enter.. so yes you might be invicible but you make yourself blind at the same time as well. so you walk arround with no clothes.. dont know where you are going.. its so useless.. I guess you would be the best hide and seek champion but everything els sucks