Mount Gagazet

Boss Fight - Biran and Yenke Ronso: Their stats are determined by Kimahri's Strength, Magic, and HP. Use Lancet to learn their Ronso Rages. Both have four Rages each. Biran has Thrust Kick, Doom, Self-Destruct, and Mighty Guard. Yenke has Fire Breath, Aqua Breath, Stone Breath, and White Wind. To learn the last Rage from each, get them under 25% HP while both are alive. If Yenke is defeated first, Biran uses Berserk. If Biran is defeated first, Yenke uses Haste. Steal Lv. 3 Key Spheres from both (common and rare). They guard each other when physically attacked; use Bulldoze to separate them and strike. Biran also uses Thunder and Blizzard. Yenke uses Fire Breath and Aqua Breath. Keep an eye on your HP and heal with Hi-Potions.

Ascending Mount Gagazet: After the Ronso fight, head right to find a chest with 20,000 Gil. Continue up the mountain; a scene will play. On the left side, find a hidden chest with two Mega-Potions.

Path Split: At the tip of the first path, approach a rock formation for a cutscene. You'll reach a point with two paths.

Northern Path: This leads to a dead end with Braska's Sphere. Collecting this, along with all other Jecht Spheres, unlocks the Messenger from the Past trophy/achievement and Auron's Tornado Overdrive.

Main Trail and Southwestern Path: Return to the main trail and take the other path. Follow it to another summoner's grave. At the next split, the southwestern path leads to a dead end with a chest containing a Defending Bracer.

Merchant Wantz: Return to the split and head in the other direction. You will encounter Wantz, a merchant and brother of O'aka. He sells equipment and Holy Waters. It is crucial to speak with him here as he is missable; if you don't, he won't appear in his later, better-stocked location.

Further Up the Mountain: Past Wantz, at the bottom of a hill, find a small hill leading to two chests containing a Lv. 4 Key Sphere and an HP Sphere. Take the other path to a third grave marker.

Save Sphere: Just uphill from the third grave marker is a Save Sphere. The next boss is ahead.