Cheapest priced copy (The Lost Caverns of Ixalan Commander): $0.99 at Card Kingdom, near mint, their price list as of .
Sorin, Lord of Innistrad 
Legendary Planeswalker — Sorin · Mythic · Dark Ascension · #142
+1: Create a 1/1 black Vampire creature token with lifelink.
−2: You get an emblem with "Creatures you control get +1/+0."
−6: Destroy up to three target creatures and/or other planeswalkers. Return each card put into a graveyard this way to the battlefield under your control.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
3 printings · $0.99 to $27.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Duel Decks: Sorin vs. Tibalt | 1 | Mythic | — | $2.29 |
| Dark Ascension | 142 | Mythic | $1.79 | $27.99 |
| The Lost Caverns of Ixalan Commander | 289 | Mythic | $0.99 | — |
4 rulings from Wizards of the Coast
- 22 January 2011You can target a token creature with Sorin, Lord of Innistrad's third ability, but it won't return to the battlefield.
- 22 January 2011If Sorin, Lord of Innistrad somehow becomes a creature, it can be chosen as a target of its own third ability. If Sorin, Lord of Innistrad is still on the battlefield when that ability resolves, it will then destroy Sorin and return him to the battlefield under your control.
- 22 January 2011If a creature with undying is destroyed by Sorin, Lord of Innistrad's third ability, the undying ability will trigger, but the creature will already have been returned to the battlefield by Sorin. The undying ability won't do anything when it resolves.
- 22 January 2011The emblems are cumulative. If you get two of them, creatures you control will get +2/+0.