Vallo is a character in Fable III who gives the quest The Key to a Greater Key, which becomes available after defeating the Crawler. He is an Auroran businessman who has a proposal for the Hero.
After The Darkness has been driven out of Bowerstone Market, one can find Vallo near the tattooist in the City of Aurora. Once approached, Vallo offers the Hero a key for 4,000 gold. He claims that the key will lead to another, greater key which in turn will open a great treasure.
If the Hero buys Vallo's key, the businessman is proven correct. His key unlocks the Crossroads of Passing, where, after solving the puzzles and defeating the Dark Minions within, the Hero can find a Gold Key.