guarDIANS and raDIANS have the last five letters in common, and as we have seen, they like threes, but they also LOVE fives! We're onto something here! Since D is the fourth letter, we are obviously looking for four sites. I means one in Roman Numerals, so it is either the first planet, or a class I gas giant. A is the first letter in Arsenic, and we have seen the Arsenic tie in on the planets, their homeworld must have had a N(itrogen) atmosphere, and the S...well the previous is all a bunch of (S)h...