The Devil listens intently, clearly impressed by your honeyed words.
He pauses, before speaking:
'Your quest is of no concern of mine, but you must be powerful indeed to have the patronage of one who can allow you to leave this place.
It seems as if we may be able to help each other out (he pauses and politely smiles, but it discomforts you as much as anything else).
You have... impressed me Bard; and as such I may not only allow you to pass with your lives, but I also offer to aid in your quest in exchange for you guaranteeing my freedom from this place.
To assist you, I offer you two deals. You may accept either, neither or both. The choice is yours. Should you accept neither however, your lives will be forfeit here in this place, and your quest will surely go unfulfilled.
Firstly, I offer the gift of a magical item I have recently come into possession of from some... less worthy than yourself (he glances at the 4 Zombies nearby). In exchange for this gift, I only ask for a promise from you to take me from this place when you leave. I ask for my freedom (his gaze falls on the Paladin). A small act of mercy and one within your power to grant.
Secondly, I also offer you the greatest gift of all. My servitude. Should you accept this second deal, you will be able to summon me to aid in your quest at any time. The price for this deal is the trifling price of your soul, to be collected on your death. A small price to pay surely, for such a noble quest as yours. (he smiles again, and you really don't like the look of it this time).
One soul to save the lives of so very many. It would be a noble act indeed to make such a sacrifice for the greater good of the multiverse, and to protect the lives of billions. A sacrifice worthy of the greatest of heroes.
You may discuss the deal among yourselves as you see fit, but I require an answer within 5 minutes (he waves his hand, and a small hourglass appears from no-where which he sets down on the ground hear the rock on which he sits).
Choose wisely, before I change my mind.
Yep.