What's Agrarian Skies? I'm assuming a mod pack of some kind obviously. What's the theme?
Modded skyblock using Hardcore Quest Mod, so it gives you a big list of tasks that you have to complete. Basically items you have to craft/collect. Relies heavily on being able to setup various farms/automation, but also forces you to learn and utilize specific mods. Main mods are Thaumcraft, Blood Magic, Thermal Expansion, Applied Energistics, Bees/Trees, Minefactory Reloaded.
On a server you can join groups so that you all share the same task list and work together towards completing them.