Cheapest priced copy (Rivals of Ixalan): $1.49 at Card Kingdom, near mint, their price list as of .
Mastermind's Acquisition 
Sorcery · Rare · Rivals of Ixalan Promos · #77p
Choose one —
• Search your library for a card, put it into your hand, then shuffle.
• Put a card you own from outside the game into your hand.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $1.49 to $11.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Rivals of Ixalan Promos | 77p | Rare | $7.49 | $11.99 |
| Rivals of Ixalan Promos | 77s | Rare | — | $5.49 |
| Rivals of Ixalan | 77 | Rare | $1.49 | $3.49 |
| Store Championships | 52 | Rare | — | $4.99 |
2 rulings from Wizards of the Coast
- 19 January 2018In a casual game, a card you choose from outside the game comes from your personal collection. In a tournament event, a card you choose from outside the game must come from your sideboard. You may look at your sideboard at any time.
- 19 January 2018There are many important moments in the story, but the most crucial—called “story spotlights”—are shown on cards. These cards have the Planeswalker symbol in their text box; this symbol has no effect on gameplay. You can read more about these events in the official Magic fiction at http://www.mtgstory.com.