The Baron Vandermir is the richest, most well-connected man in town since the Duke departed for the war.
First, he can provide the party with accomodations and a safe house. His manor is not only opulently appointed with every amenity known to man, it also has a secret tunnel that runs from Calliver Green to a small nondescript hovel at the base of the hill. The PCs can come and go at will without anyone observing their movements.
Second, he can grant the PCs almost total legal immunity in Farholde. As long as they are not caught redhanded doing some henious deed his word that they were with him excuses every suspicion of their involvement in a crime. Obviously this should be a last resort and the group should be careful - the last thing they need is a squad of Mitran Inquisitors taking an interest in Farholde.
Third, he has contacts among the shadier merchants who operate in and around Farholde. He can give the PCs access to poisons and more sinister magic items.
Fourth, the Baron is a sorcerer specialized in the enchantment school. He is also a negotiator without peer. If the PCs need someone charmed, bribed or persuaded there are few more qualified people in all of Talingarde to aid them than the Baron.
Fifth, the Baron runs an orphanage should the group need a few sneaky lookouts, thugs or pickpockets! He can introduce them to the Headmaster of the Orphanage, Bergill Mott.
What the Baron will not do is aid them in finding or clearing out the Horn of Abaddon. He has volunteered to help them, not fight their battles. He also has no desire to die in some cursed daemonic temple.