Before attempting this mission it is advisable to train up the team more than for the previous missions put together: leveling up all flying units (useful for the first part of the mission) and, in particular, getting Grotius's hp to around 65, leveling up Niven's attacks so that his Fling deals 30-40 damage, generally leveling up all teammates to have around 45-55 hp, leveling up all teammates to deal around 15-20 damage, it is also crucial to get Shadow Resistance to all teammates that can get it (all Shadowlings, except for Niven). Training up the Hero to have Vengeance and have high hp (around 50) could come in very handy, as well as having the Green Orb(gives a boost to speed). After completing mission 5, Tastidian will send you to rescue General Darkeye, who is stranded on an island