legendary key is pretty random. i found it while replaying levels 13-24 to complete missions (which are also pretty random with finding the blue storage devices). I found using the absorb damage shield at max upgrade was the best defense against entity; psion wave uses too much energy even at max and doesnt do enough damage to win that endurance badge. just use the shield whenever you get really weak and keep firing nukes.
@lightwired active is a party skill so only one member of your group should be focused on it--you still get the same amount of ap regardless of how many members have it. it's just a waste of skills to have everyone in the party maxing it.
 "Ghost Guidance"){kind=icon}
 "Mushroom Madness 2"){kind=icon}
 "Bloons Super Monkey"){kind=icon}
 "Endless Zombie Rampage 2"){kind=icon}
 "Frontier"){kind=icon}
 "Valthirian Arc"){kind=icon}
 "Enigmata 2: Genu's Revenge"){kind=icon}
 "Dead Frontier: Outbreak 2"){kind=icon}
 "Elona Shooter"){kind=icon}
 "Balloon in a Wasteland"){kind=icon}
 "Straw Hat Samurai 2"){kind=icon}
 "My Pet Protector 2"){kind=icon}
 "Chaos of mana"){kind=icon}
 "The Necronomicon"){kind=icon}