Siege On Abbadon
If they need to strike, they need to strike now. He can only be killed outside of Hell. She will get them, if you can ensure she is not harmed once she takes his position in Hell. There is an opening now, and we need to strike.
He is protected by a pain link spell upkept by an army of slaves and mages. They are weak, but protected. If the spell is removed, he will retreat immediately. We will need one group to infiltrate the fortress, and one to take him out. She can act as a messanger.
His mages reside in the Bleeding Orchard. Inside a pyramid overlooking the fields.
He is otherwise residing offshore on an island. He can be angered, and will need to either be assaulted to remove his army force.