You'll control Snow in the House of Stairs, where your goal is to hit a particular glowing apparatuses. Aside from the Potions behind Snow, there's nothing of interest in any of the side paths here. Snow will be fighting alone, but his high HP total makes the battles here fairly easy. You'll return here after visiting Lightning and Sazh's storyline for a bit, finding a second pair of Potions and proceeding through one more fight.