I'm really curious how much the siren will be. I have one from when it was a prize in a monster hunt / leaderboard event, and I absolutely love her drops!
(She has a 6-hour timer and drops either 4 earth wisps, 2 wisp lanterns, 2 trade tickets or 1 expansion permit each collection. Of course the earth wisps are by far the most common drops, but at 4 per collection they are nothing to sneeze at. I also get 2 lanterns quite regularly, and the other drops occasionally/rarely.)