Instead of entering the world of Worm as a Host you'll become a Shard instead. Your Host is determined by your choices in the Character section and the Perks and Drawbacks apply to them instead (with the exception of the ones that affect their Shard or the World). If you become the shard of an existing parahuman you take over their existing shard instead of becoming a new one. Your hosts can reach your nesting dimension through portals and teleportation with your permission.