The Spawn Fortress
At the center of the world, it's a place to chill during pre-game setup, a possible battleground for the final confrontation, and on the lower level, is an empty end portal, just in case you need to go to the end while the world border is shrinking.
Better Questing Provides Guidance
A breakdown of how the modpack works/can-work is provided by way of Better Questing's questbook, which you will spawn in with initially.