In the upper left corner of the chart, there is an unnamed island. There is a vampire demon's tomb on the island, and next to it is the Crooked Branch Forest.
On the 16th of every month, there will be vampire demons there to perform ritual blood sacrifices. If you act before the blood sacrifice, you can save a crew member. If you wait for the blood sacrifice before taking action, you can get the blood-sucking demon's ceremonial sword - the blood-red giant sword.
This sword is at the legendary level when you get it. You only need to upgrade two side enchantments. It is very powerful, even stronger than the Whisper of the Endless Road inherited from one generation.
PS: Endless Whispers is formed early, and the Blood Red Sword is already in the mid-to-late stage when it can be used. Late formation is its shortcoming. It’s a bit difficult in the early stages.