Cheapest priced copy (Guilds of Ravnica): $0.49 at Card Kingdom, near mint, their price list as of .
Omnispell Adept 
Creature — Human Wizard · 3/4 · Rare · Guilds of Ravnica · #49
{2}{U}, {T}: You may cast an instant or sorcery spell from your hand without paying its mana cost.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Guilds of Ravnica | 49 | Rare | $0.49 | $0.49 |
3 rulings from Wizards of the Coast
- 5 October 2018If a spell has {X} in its mana cost, you must choose 0 as the value of X when casting it without paying its mana cost.
- 5 October 2018If you cast a spell “without paying its mana cost,” you can’t choose to cast it for any alternative costs. You can, however, pay additional costs, such as kicker costs. If the card has any mandatory additional costs, such as that of Severed Strands, those must be paid to cast the card.
- 5 October 2018You may cast a sorcery this way even if it’s not your turn.