Think of these cards like investing in fine art or vintage winesvalue grows as supply diminishes
Akroma, Vision of Ixidor & Bruse Tarl, Boorish Herder Akroma, Vision of Ixidor & Falthis, Shadowcat Familiar Akroma, Vision of Ixidor & Anara, Wolvid Familiar Bruse Tarl, Boorish Herder & Jeska, Thrice Reborn - Use Bruse to give double-strike to a creature with evasion, then use Jeska triple that creature's damage
It's powerful because it has nasty potential depending on the cards you pair it with
However, recent trends in the Pokmon TCG have made collecting all the Ultra Rares in a set a near impossible task
though it plays incredibly well with merfolk, I wouldnt limit it to a typal card
Kuriboh Of all the monsters that went through Yugi's deck, perhaps no other was more surprisingly recurring than Kuriboh