Minecraft: Twilight forest

So i tried a new world mod today and i entered the Twilight forest. This way my view at the time. I like the lightning bugs on the tree. Think thats what they're called. Also like how even though the sun is up, the stars are out too.

But there was a kind of obsidian pillar behind me which kinda confused me but since i like to download first, read second, i didn't think much of it.