Cheapest priced copy (Core Set 2020 Promos): $1.99 at Card Kingdom, foil, near mint, out of stock, their price list as of .
Gargos, Vicious Watcher 
Legendary Creature — Hydra · 8/7 · Rare · Core Set 2020 · #172
Vigilance
Hydra spells you cast cost {4} less to cast.
Whenever a creature you control becomes the target of a spell, Gargos fights up to one target creature you don't control.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
5 printings · $1.99 to $9.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Core Set 2020 | 172 | Rare | $2.29 | $3.49 |
| Core Set 2020 Promos | 172 | Rare | — | $1.99Out of stock |
| Core Set 2020 Promos | 172p | Rare | $3.49 | $4.49 |
| Core Set 2020 Promos | 172s | Rare | — | $5.99 |
| Secret Lair Drop | 1329 | Rare | — | $9.99 |
8 rulings from Wizards of the Coast
- 12 July 2019Gargos's cost-reduction ability affects only generic mana in a Hydra's cost. For example, if you cast a Hydra spell with mana cost {2}{G}{G}{G}, it will cost {G}{G}{G} to cast, not {G}.
- 12 July 2019If the target creature is an illegal target when Gargos's last ability tries to resolve, the ability doesn't resolve. If Gargos is no longer on the battlefield, the target creature won't deal or be dealt damage.
- 12 July 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 (such as that of Gargos). The mana value of the spell remains unchanged, no matter what the total cost to cast it was.
- 12 July 2019If a spell has {X} in its mana cost, you choose the value for X before applying cost reductions. For example, if you cast a Hydra spell with mana cost {X}{G}{G} and choose for X to be 6, you pay {2}{G}{G}. Any of that Hydra's abilities that refer to X still uses 6 as the value for X regardless of what you actually paid.
- 12 July 2019Gargos's triggered ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.
- 12 July 2019Gargos's controller chooses which creature (if any) Gargos will fight, not the controller of the spell.
- 12 July 2019Gargos's cost-reduction ability applies only while it's on the battlefield. Gargos doesn't reduce its own cost.
- 12 July 2019If a spell targets one creature you control multiple times, Gargos's ability triggers once. If that spell targets multiple creatures you control, Gargos's ability triggers once for each of those creatures.