Cheapest priced copy (Forgotten Realms Commander): $0.49 at Card Kingdom, near mint, their price list as of .
Dream Pillager 
Creature — Dragon · 4/4 · Rare · Forgotten Realms Commander · #125
Flying
Whenever this creature deals combat damage to a player, exile that many cards from the top of your library. Until end of turn, you may cast spells from among those exiled cards.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
5 printings · $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Forgotten Realms Commander | 125 | Rare | $0.49 | — |
| Commander 2015 | 25 | Rare | $0.49 | — |
| Commander Legends: Battle for Baldur's Gate | 791 | Rare | $0.49 | — |
| Commander Anthology Volume II | 93 | Rare | $0.49 | — |
| Starter Commander Decks | 139 | Rare | $0.49 | — |
5 rulings from Wizards of the Coast
- 4 November 2015Any cards you don't cast will remain exiled.
- 4 November 2015The cards are exiled face up.
- 4 November 2015If you cast an instant or sorcery card this way, it will go to your graveyard after it resolves, fails to resolve, or is countered. It won't return to exile.
- 4 November 2015Exiling all the cards from your library this way won't cause you to lose the game. You'll lose only if you attempt to draw a card from an empty library.
- 4 November 2015Casting a card this way follows the normal rules for casting the card. You must pay its costs, and you must follow all applicable timing rules. For example, if one of the cards is a creature card, you can cast that card only during your main phase while the stack is empty.