User blog comment:Trainsparency/2019 Spook and Sinister Hunting Thread/@comment-35996958-20191009124457

I don't know why December spook is a challenge still. I don't think it will ever return. Since they were all found in 2015, and Spook/Sinister trees were introduced in 2015, it seems like there was some sort of glitch that made them start spawning again. Furthermore, none have been found since then, making it seem like it was patched for all years following.