Cheapest priced copy (Throne of Eldraine): $1.29 at Card Kingdom, near mint, their price list as of .
The Cauldron of Eternity 
Legendary Artifact · Mythic · Throne of Eldraine · #352
This spell costs {2} less to cast for each creature card in your graveyard.
Whenever a creature you control dies, put it on the bottom of its owner's library.
{2}{B}, {T}, Pay 2 life: Return target creature card from your graveyard to the battlefield. Activate only as a sorcery.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $1.29 to $6.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Throne of Eldraine | 82 | Mythic | $1.29 | $1.99 |
| Throne of Eldraine | 352 | Mythic | $3.99 | $6.99 |
| Throne of Eldraine Promos | 82p | Mythic | $3.99 | $2.99 |
| Throne of Eldraine Promos | 82s | Mythic | — | $6.49 |
3 rulings from Wizards of the Coast
- 4 October 2019To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.
- 4 October 2019Once you announce that you're casting a spell, no player may take actions until the spell has been paid for. Notably, opponents can't try to change by how much a relic's cost is reduced.
- 4 October 2019The cost reduction ability reduces only the generic mana in the relic's cost. The colored mana must still be paid.