Drink some water from the waterfall to replenish you HP and MP. Go in the direction that Jiro pointed. After a scene you will have to fight two tigers. They deal whopping damage, but have little HP themselves - if one of your heroes gets knocked out, just resurrect him. It's a quick battle. When you defeat them, a true boss appears.
Boss - Dullahan
This monster's attacks are relatively weak, but you need to weaken him first in order to deal serious damage yourself. It pays to use Ground magic on him. In about 3/4 of the battle, the monster will lower his defences and increase his attack power. Monitor your health so that you don't get KO'd and steadily attack him until he falls.
Talta Village Camp
When you're near the campfire, look around the area. There's a shop in one of the tents. Enter Jiro's tent (near the save point) to see a scene. Talk to Fushira. Save your game when you're prompted.
Your goal now is to escort the caravan on its way to Jibral Castle. It's not a difficult sequence to beat, but it definitely IS difficult to unlock an achievement here. In order to do that, you can't let the wagons take a single hit, even despite that you have some repair kits that bring back 20% health to the caravan. Don't use your battle circle here, better stick to attacking opponents by pressing X. It's also important to eliminate rats in the first place, and then tigers. The monsters always appear in the same spots, so if you don't manage to unlock the achievement for the first time, just learn their locations and try again.
Achievement is unlocked only when the caravan doesn't take a single hit through the entire scene.
Fat Pack Rat ahead of the convoy
Fat Pack Rat between the wagons
A chest with Thorn Branch
Fat Pack Rat ahead, Steel-Eating Tiger between the wagons
Two stones to knock over
Another two stones. When you knock the second one down...
... Fat Pack Rat to the left and to the right of the convoy
Fat Pack Rat at the back, Fat Pack Rat between the wagons, Steel-Eating Tiger ahead
One stone; when you knock it over ...
... Fat Pack Rat to the left of the first wagon, Steel-Eating Tiger to the right of the first wagon, Fat Pack Rat between the wagons
One stone. When you knock it over ...
2x Fat Pack Rat ahead of the convoy (use battle ring here).
When you reach a clearing, a cut-scene will commence, after which you will be up against 4 tigers at once.
Boss - Four Steel-Eating Tigers
You know what these tigers are capable of by now. They use their Bite ability every two turns, which instantly kills one party member. Use Ground and Water spells, as well as any other that deals damage to the entire row of enemies at once (you can use some Flawless gems here).