So in Chapter 53, Secrets of the Goblins, Tusk figures it out. What the Trade Prince was after were the Laws and he planned to sell them to the highest bidder, as would most any Goblin. (Remembering that the only thing worse than a Goblin is a Dark Elf) -
Tusk then talks to Dortsa and the plan is hatched and it is a daring one. They lay the ground work for a return to the home world, the World of the Dark Elves and Goblins. Their purpose is to lure Queen Sabrenella and as many Dark Elves to Medelia. This would be their revenge.
Now there is a tantalizing bit of information that I mention here. Dortsa brings up the subject. The Dark Elves are supposed to be immortal. But, the Trade Prince did his homework. They really are not once they come to the World of the Humans. Remember, that Dark Elves turn to stone once they are exposed to light - far from being immortal. But the Elves don't think this is so as it pertains to Medelia. (the line of reasoning is for another day)
So the plot is hatched in this chapter. Tusk and Dortsa plan to return to their world. They will have to convince their Clan Counsel that the prize to end all prizes is up for grabs. (remembering that the Clan Counsels are ruled by the Dark Elves with representation by the Trade Princes - who are Goblins)
All of this will be played out in Book Two......you'll love it