To be honest, I'm surprised that Night Souls are still purchasable with Blood Fragments. I believe Kaz said awhile back that when Part 2 of the mega-event began, the Night Souls for Blood Frags would switch to be the Part 2 featured soul (Shrieking Soul). But, that apparently didn't happen.
Update: Below is the post I referenced . . .
https://forum.ironmaidenlegacy.com/s...ll=1#post87969
Update #2: I have re-read this post and those leading up to it several times, and now it's unclear to me if the Night Souls for Blood Frags was going to rotate as well. Maybe we can get clarification from the devs. If it isn't going to rotate, you might have time to get The Killer, which I would definitely do. Maybe the devs will give us the end date, so you can do the math.