Your trek through the ark begins in earnest here. You will most likely want to include Fang or Snow in your party to act as a Sentinel, because many of the enemies here hit very hard and you'll need one. All of the available party members will have their uses here—there are enemies susceptible to Deprotect and Deshell for Vanille as well as Curse and Slow for Fang. Relying on a Sentinel makes Hope's defensive buffs a bit less important, but he's still a powerful Ravager. Mix and match to see what works for you. Note that you can't take Lightning out of the leader spot until after your first battle. However, winning that battle will also unlock all six Roles for every party member!