When Yan Xing first agreed to Duan'er's request, allowing the grain exchanged by Red Mud Wetland for agarwood to be stored in Eternal Domain, he had been considering the feasibility of establishing a grain bank.
If all the Werewolf Tribes on the southern edge of Thunderous Swamp stored the grain they obtained from Eternal Domain here, then anyone who dared to covet Eternal Domain would undoubtedly be provoking these thirty-plus Werewolf Tribes.
This metaphor might not be entirely appropriate, but the meaning is roughly the same.
The werewolves would definitely fight desperately for their own grain.
Looking further into the future, Yan Xing's decision to permit the werewolves to use their stored grain to purchase goods from Eternal Domain also solidified the role of Eternal Domain's grain as a common equivalent, effectively becoming a "currency" that could circulate within the Werewolf Tribes.