FTB Skies is a modpack set high up on a floating island, where there's no land in sight and every bit of progress comes from what you can gather and build yourself. You start with limited resources, so survival means being careful, making smart use of what you have, and slowly turning that tiny island into something much bigger.
It's not an easy start either. Hostile mobs are always around to make things harder, and the whole pack is built around that constant struggle to keep moving forward. As you get further in, you'll start mixing magic and technology too, from powerful spells to advanced machinery, so there's always something new to work toward.
Quest guidance helps keep things moving and gives you a clear idea of what to do next, which makes it easier to stay focused while you expand into the clouds. If you like skyblock-style progression with survival pressure, a bit of PvP, and a good mix of magic and tech, FTB Skies is a solid one to jump into.