For this mission, a little training can be useful (e.g. getting Duvalier Feedback and the Blood Orb could come in handy). After talking to Griffin, head to the Marid Campgrounds and speak to the Chief Hamzah. You'll find him unwilling to help you fight the Cult, but if you suggest to root out a problem with the Bandits, then he'll provide you with a guide, who'll get your group to Bandit Territory. You'll face 4 battles.
Battle: Desert Ambush 1Edit
In the first one, watch out for the Bandit Longbowman units in the north of the map. Use Griffin to block the bandits in the middle of the map between the rocks, whilst you can send Luca to exterminate the bowmen on the left side of the map (Rahel can help out too). Use Set to heal Griffin and maybe send Duvalier to plug in the second entrance to block the Bandits from attacking your formation from the top. Taking care to heal all units, this map should not present much of a problem (btw, watch out for the top, right-corner Bandit- he respawns after a few turns, so you better kill him last).
Battle: Desert Ambush 2Edit
In the next map, one way is to send Griffin to the north, to take on most of the damage from the top formation, while sending Duvalier, along with Arman, Luca, and Rahel to quickly deal with the enemy formation on the left hand side. In the next few turns, send Arman through the left side of the map to deal with the second Bandit Longbowman, send Rahel to the very right of the map to deal damage to units across the rift and use Duvalier and Griffin to attack the enemy formation through the gap.
Battle: Desert Ambush 3Edit
In the next battle, try to kill off as many Bandit Raiders as possible on your very first turn, or, at least, position your units in such a way as to be able to fend off their first attack- making a wall of Griffin and Arman for the bottom two Raiders could help. Then you can use all the ranged units to deal damage to the raiders, while sending Duvalier and Arman to kill off the bowmen before they come close enough to help the Raiders. Watch out for Bandit Longbowmen at the top of the map- simply stay out of their shooting range and you won't even have to kill them. The two Bandit Bowman units on the left respawn, so that after clearing the bottom of the map of all enemies for the first time, for a column from Griffin, Luca, and Rahel to tackle the stone blocking the entrance to the cave, while keeping Arman, Duvalier, and Set to the left of the column- this will allow them to deal with rewspawning Bandit Bowmen and allow Set to heal any wounded units.
Battle: Boss: Jabbar the BanditEdit
After this battle ends, comes the final boss battle with Jabbar, the Bandit Leader. Here, great caution must be used not to lose many teammates from the beginning. Using teammate blocking techniques (i.e. placing another teammate between a wounded teammate and the enemy) could come in very handy, but watch out for the boss' Slash attack and for the two respawning units on the top corners of the map. One way to proceed is to split the team in two main parts, let one part (say, Griffin, Duvalier, Luca) take on the enemies on the left hand side of the map, whilst Rahel and Set can slowly proceed upwards on the right side of the map. Meanwhile, Arman can circle around on the right side of the map and backstab any units wounded by Rahel. When the left hand side team cuts through to Jabbar, it's best to heal Griffin as much as possible, whilst keeping Set out of harm's way and use all other teammates to get rid of any enemy Bandits remaining (sending Duvalier to the far left to do the clean-up could help and try to use Feedback whenever possible). When facing Jabbar, try not to attack him from up front- he counterattacks with his Melee attack dealing a lot of damage. At this point using the Hero and Arman to kill off the respawning units might be a good idea, as it will take them several turns to respawn, which can be used to assemble all teammates and take on Jabbar. Chances are, Jabbar will get to Griffin long before his Bandits' are all disposed of, so try positioning your units in such a way as to block them access to any unit that is in direct confrontation with Jabbar, and if that can't be helped, block as many as you can (especially watch out for the Bowmen- they can be the most unpredicatble). This might take more than one try, but eventually you should be able to bring down Jabbar and that should finish the fight (one last suggestion- Luca's Transfer to Set could help more than one teammate stay alive for a bit longer).