Cheapest priced copy (Jumpstart 2022): $0.49 at Card Kingdom, near mint, their price list as of .
Magmatic Channeler 
Creature — Human Wizard · 1/3 · Rare · Zendikar Rising · #349
As long as there are four or more instant and/or sorcery cards in your graveyard, this creature gets +3/+1.
{T}, Discard a card: Exile the top two cards of your library, then choose one of them. You may play that card this turn.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
5 printings · $0.49 to $0.59 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Jumpstart 2022 | 571 | Rare | $0.49 | — |
| Zendikar Rising Promos | 148p | Rare | $0.49 | $0.49 |
| Zendikar Rising Promos | 148s | Rare | — | $0.59 |
| Zendikar Rising | 148 | Rare | $0.49 | $0.49 |
| Zendikar Rising | 349 | Rare | $0.49 | $0.49 |
4 rulings from Wizards of the Coast
- 25 September 2020You’ll still pay all costs for a spell cast this way, including additional costs. You may also pay alternative costs if any are available.
- 25 September 2020If you don’t play the exiled card you chose, it remains exiled. The card you didn’t choose remains exiled whether you play the chosen card or not.
- 25 September 2020Magmatic Channeler gets just +3/+1 from its first ability, no matter how many instant and sorcery cards are in your graveyard beyond the fourth.
- 25 September 2020You choose which card you’ll be allowed to play this turn while Magmatic Channeler’s ability is resolving, but you must follow the normal timing permissions and restrictions for the card when you play it. If it’s a land, you can’t play it unless you have land plays available.