A simple idea really.
Mermaid gems belong to particular mermaid items.
Collect all the gems and insert them into treasure items such as mermaid urns, runes etc to sell for a bigger profit.
However...
Find mermaid weapons such as gem less staffs etc in the sea, swords and such, uncovered from fishing, finding on islands, in caves and underwater etc..... Place a gem inside the empty socket (as if it's a shroud breaker) and have an elemental weapon with finite uses before it breaks, similar to how flame skulls work
Each colour can represent an element.
Red = Fire.
BLUE = Water
Green = Poison.
You have only a few uses until it breaks. You can also choose to sell them if you wish.
