If you're really determined to acquire things like merfolk and siphonophore crystals, it's not like they're impossible to buy.
But there's just so few of them.
Even though only a part of the city defense magic array requires them, expanding it to encompass the entire Fungus Castle would require no small amount.
The core function of this portion of the magic array is to slowly absorb free-floating ice elemental energy from the environment and store it up, to be released in one go to form a large-scale frost shock when needed.
It's quite suitable for the Fungus Castle.
Omitting this section isn't impossible, but since the Fungus Castle is the core foundation of Lin Jun's operations, provided the conditions allow it, he hopes to make it more complete.
Originally, if the archipelago was still around, these materials could probably be gathered through trade, just at the cost of some extra gold coins.
However, after the mist, the archipelago lost contact with the continent.
