Cheapest priced copy (Commander Anthology Volume II): $2.79 at Card Kingdom, near mint, their price list as of .
Wrexial, the Risen Deep 
Legendary Creature — Kraken · 5/8 · Mythic · Worldwake · #120
Islandwalk, swampwalk (This creature can't be blocked as long as defending player controls an Island or a Swamp.)
Whenever Wrexial deals combat damage to a player, you may cast target instant or sorcery card from that player's graveyard without paying its mana cost. If that spell would be put into a graveyard, exile it instead.
Legal inCommanderModernLegacyVintage
Not legal inBrawlStandardPioneerPauper
5 printings · $2.79 to $19.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander Anthology Volume II | 171 | Mythic | $2.79 | — |
| Commander 2011 | 239 | Mythic | $2.99 | — |
| New Capenna Commander | 359 | Mythic | $2.79 | — |
| Secret Lair Drop | 584 | Mythic | — | $9.49 |
| Worldwake | 120 | Mythic | $2.79 | $19.99 |
4 rulings from Wizards of the Coast
- 1 March 2010If you are unable to cast the targeted card (there are no legal targets for the spell, for example), nothing happens when the ability resolves, and the card remains in its owner's graveyard.
- 1 March 2010If you cast a card "without paying its mana cost," you can't pay any alternative costs. On the other hand, if the card has additional costs (such as kicker or multikicker), you may pay those.
- 1 March 2010If you cast the targeted card and it would be put into its owner's graveyard from the stack for any reason (either because it resolves or because it's countered), that card is exiled instead.
- 1 March 2010If you want to cast the targeted card, you cast it as part of the resolution of Wrexial's triggered ability. Timing restrictions based on the card's type are ignored. Other restrictions are not (such as "Cast [this card] only during your end step").