In the 2019 'Pokémon Card Game Sun & Moon: Booster Pack—Sky Legend,' a special rarity known as TR (Trainer Rare) was introduced within the Sun & Moon series. These TR cards had designs slightly rarer than your regular Common and Rare Trainer cards. What makes them a treasure for collectors is that they feature original character illustrations, much like the highly sought-after SR cards. It's like finding a unique piece of Pokémon art within your card collection!