A long line of magical beasts had returned outside Blackmoon Town, carrying many valuable plants and ores on their backs. Many of those plants and ores were of the platinum tier. They were the results of Watson's fusion with more than half of the Misty Forest some time ago.
Watson had intended to leave the platinum-tier ores and herbs which he had fused at the Misty Forest. He had wanted to wait until the supplies in Blackmoon Town were depleted before heading out to get them. However, he changed his mind due to the goldbiter rats.
The goldbiter rats could eat everything in their path. If they did not carry those goods back to Blackmoon Castle, they would be gone in a matter of days.