magic cards rare how to tell Most Valuable 15 most valuable and rare

It could be a bonus card randomly inserted into certain Secret Lairs (a la the Smothering Tithe from Spongebob drops), or maybe it's an add-on for spending a certain amount on the Secret Lair website, which shouldn't be that hard to do with these drops

Flying As Talion, the Kindly Lord enters the battlefield, choose a number between 1 and 10. Whenever an opponent casts a spell with mana value, power, or toughness equal to the chosen number, that player loses 2 life and you draw a card

The last Ghost Rare is now speculated to be Dark Magician Girl in OGC artwork form

After that, shift the control of this card to your opponent