Tucked in fish-bait
Bardeelus managed to make a deal in a short time, as these people from the sect were direct. They knew what they wanted, communicated it bluntly and managed to reach a mutual understanding.
Tumira had even repeated, "What we want is as simple as what cave-people wanted ages ago. The sea is dangerous right now, and we need you to make it less dangerous."
In context, they explained that there were these weird fish in the country's ocean, which had dark powers. Some resurrected dangerous fish to their aid, which was problematic, because they could even resurrect whole whales!
Animals like that were dangerous to begin with, but paired with coordinated attacks, they were a problem. Many trade-routes across the sea were put on halt, and fish were destroying the economy!