Siege of the Overworld is currently an expiremental pack that is a hybrid pack between skyblock and normal surivival. The reason such a hybrid can exist is that the overworld is very hostile where the skyblock is safe. in this pack, you can power machines, fight mobs, do tech trees, etc. the many mods (in future versions) will interact with each other, so expect interactions like throwing coal into a mana pool, and getting an item that powers machines. the pack is currently in beta so expect changes, but the core philosophy should remain the same.