Cheapest priced copy (Dominaria United): $0.35 at Card Kingdom, near mint, their price list as of .
Tolarian Terror 
Creature — Serpent · 5/5 · Common · Dominaria United · #72
This spell costs {1} less to cast for each instant and sorcery card in your graveyard.
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
Legal inCommanderBrawlStandardPioneerModernLegacyVintagePauper
3 printings · $0.35 to $1.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dominaria United | 72 | Common | $0.35 | $1.99 |
| Foundations | 167 | Common | $0.35 | $0.79 |
| The List | DMU-72 | Common | $0.35 | — |
2 rulings from Wizards of the Coast
- 8 November 2024Tolarian Terror's first ability can't reduce its cost below {U}.
- 8 November 2024To 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 (such as that of Tolarian Terror). The mana value of the spell is determined by only its mana cost, no matter what the total cost to cast that spell was.