I went on the NJ satelite diplomatic mission on day 7 and lo and behold, I encountered a SIREN!! 450hp Siren in week 1?! Has anyone encountered Sirens this early before?
Not the Siren, but heavily armored (evolved on most body parts) Arthrons on that mission. Solution? Don’t do diplomatic mission so early. 
Yeah man, got myself a Siren. I usually get to Aligned with either Anu or NJ by the end of the first week and by the second week, I should get to supportive or even aligned on the other. However, this is the first time I got myself a Siren this early in so many playthroughs at Hero diff.
Not to say the Siren posed any threat though. To be honest, she died right after mind controlling one of my guys. So she did not real harm at all. Saw it from a far and since I have a team of 5 Heavy Cannons, it didn’t take me long to take her down.