Cheapest priced copy (Theros Beyond Death): $0.35 at Card Kingdom, near mint, their price list as of .
Brine Giant 
Creature — Giant · 5/6 · Common · Theros Beyond Death · #44
Affinity for enchantments (This spell costs {1} less to cast for each enchantment you control.)
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Theros Beyond Death | 44 | Common | $0.35 | $0.49 |
3 rulings from Wizards of the Coast
- 24 January 2020Once 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 Brine Giant's cost is reduced.
- 24 January 2020To 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 Brine Giant). The mana value of the spell remains unchanged, no matter what the total cost to cast it was.
- 24 January 2020The cost reduction ability reduces only the generic mana in Brine Giant's cost. The colored mana must still be paid.