Lunar Subterrane, Ahriman 6666, grey / yellow, Colorado shooting, and more
When I get treasure on the Lunar Subterrane, the grey items like the Rat's Tail are now yellow! That hasn't happened before to my knowledge... or maybe it's because I finally cleared out my inventory, and can see this!
After defeating an Ahriman floating eye, you get 6666 experience points!
Your party gives the Rat Tail to the tail collector at the Adamant Grotto near Mythril for Adamantite:
Later, they give the Pink Tail (a super-rare drop from the Flan Princess in the Lunar Subterrane) to him for the Adamant Armor: