Cheapest priced copy (Ravnica Allegiance): $11.99 at Card Kingdom, near mint, their price list as of .
Prime Speaker Vannifar 
Legendary Creature — Elf Ooze Wizard · 2/4 · Mythic · Ravnica Allegiance · #195
{T}, Sacrifice another creature: Search your library for a creature card with mana value equal to 1 plus the sacrificed creature's mana value, put that card onto the battlefield, then shuffle. Activate only as a sorcery.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $11.99 to $34.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ravnica Allegiance | 195 | Mythic | $11.99 | $34.99 |
2 rulings from Wizards of the Coast
- 25 January 2019If a creature or a creature card in your library has {X} in its mana cost, X is considered to be 0.
- 25 January 2019Tokens that aren't a copy of something else don't have a mana cost. Anything without a mana cost normally has a mana value of 0.