$info cerberus, but basically its one of the 2 members of the hell team. They offer mutually beneficial deals. In this case you can choose to protect yourself, but doing so will sell your soul. Having lost your soul doesn't cause you any issues, but you won't be able to make deals with hell team again afterwards.
For Hell team, getting everyone's soul is their goal (and additionally they can use souls to protect themselves / attack others), so taking an offer like this from the hell team is something that should be considered carefully.