Gargos, Vicious Watcher

Text:

Vigilance
Hydra spells you cast cost less to cast.
Whenever a creature you control becomes the target of a spell, Gargos, Vicious Watcher fights up to one target creature you don't control.

Rulings:

• 7/12/2019 To 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 converted mana cost of the spell remains unchanged, no matter what the total cost to cast it was.
• 7/12/2019 Gargos’s cost-reduction ability affects only generic mana in a Hydra’s cost. For example, if you cast a Hydra spell with mana cost <img src="/Handlers/Image.ashx?size=small&amp;name=2&amp;type=symbol" alt="2" align="absbottom" /><img src="/Handlers/Image.ashx?size=small&amp;name=G&amp;type=symbol" alt="Green" align="absbottom" /><img src="/Handlers/Image.ashx?size=small&amp;name=G&amp;type=symbol" alt="Green" align="absbottom" /><img src="/Handlers/Image.ashx?size=small&amp;name=G&amp;type=symbol" alt="Green" align="absbottom" />, it will cost <img src="/Handlers/Image.ashx?size=small&amp;name=G&amp;type=symbol" alt="Green" align="absbottom" /><img src="/Handlers/Image.ashx?size=small&amp;name=G&amp;type=symbol" alt="Green" align="absbottom" /><img src="/Handlers/Image.ashx?size=small&amp;name=G&amp;type=symbol" alt="Green" align="absbottom" /> to cast, not <img src="/Handlers/Image.ashx?size=small&amp;name=G&amp;type=symbol" alt="Green" align="absbottom" />.
• 7/12/2019 If a spell has <img src="/Handlers/Image.ashx?size=small&amp;name=X&amp;type=symbol" alt="Variable Colorless" align="absbottom" /> 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 <img src="/Handlers/Image.ashx?size=small&amp;name=X&amp;type=symbol" alt="Variable Colorless" align="absbottom" /><img src="/Handlers/Image.ashx?size=small&amp;name=G&amp;type=symbol" alt="Green" align="absbottom" /><img src="/Handlers/Image.ashx?size=small&amp;name=G&amp;type=symbol" alt="Green" align="absbottom" /> and choose for X to be 6, you pay <img src="/Handlers/Image.ashx?size=small&amp;name=2&amp;type=symbol" alt="2" align="absbottom" /><img src="/Handlers/Image.ashx?size=small&amp;name=G&amp;type=symbol" alt="Green" align="absbottom" /><img src="/Handlers/Image.ashx?size=small&amp;name=G&amp;type=symbol" alt="Green" align="absbottom" />. Any of that Hydra’s abilities that refer to X still uses 6 as the value for X regardless of what you actually paid.
• 7/12/2019 Gargos’s cost-reduction ability applies only while it’s on the battlefield. Gargos doesn’t reduce its own cost.
• 7/12/2019 Gargos’s controller chooses which creature (if any) Gargos will fight, not the controller of the spell.
• 7/12/2019 If 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.
• 7/12/2019 Gargos’s triggered ability resolves before the spell that caused it to trigger. It resolves even if that spell is countered.
• 7/12/2019 If 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.