tortoise shell
瑇 centers on tortoise shell, specifically the material from hawksbill turtles used for ornaments and crafts.
瑇 combines 王 (jade/precious stone) with 毒, which likely contributes the sound タイ. The character was created to refer to tortoise shell, a valuable material similar to jade.
The 王 (jade) radical on the left suggests a precious material, and 毒 (poison) on the right hints at something exotic or dangerous. Picture a beautiful tortoise shell ornament that looks like jade but comes from a creature that might be poisonous.
For タイ, imagine a tortoise shell tie clip: tie -> タイ, and the shell is polished like jade.