"A slightly 'light texture', easily absorbed by other strange tales; and a slightly 'heavy texture', not easily absorbed by other strange tales."
The former is what Kamiyagawa refers to as "Strange Tale Relics."
And the materials from the two Dark God Thunder Dukes are not easily absorbed by other strange tales, so they belong to the latter. Generally used for creating extraordinary tools or weapons.
For example, [The Skin and Bones of the Earthquake Thunder Duke] alone, judging by the description in its appraisal, could surely be made into a grand drum that summons thunderbolts.
"However... both these divine remnant materials carry divinity. Instead of making them into weapons or tools, their better use would indeed be as the core for constructing shrines."
If [The Skin and Bones of the Earthquake Thunder Duke] were used for shrine construction, it would surely imbue the shrine with thunderbolt authority.
