Young Gold Dragon

Armor Class 18 (natural armor)
Hit Points 178 (17d10 + 85)
Speed 40 ft., fly 80 ft., swim 40 ft.

Saving Throws Dex +6, Con +9, Wis +5, Cha +9
Skills Insight +5, Perception +9, Persuasion +9, Stealth +6
Damage Immunities fire
Senses blindsight 30 ft., darkvision 120 ft., passive Perception 19
Languages Common, Draconic
Challenge 10 (5,900 XP)

Amphibious. The dragon can breathe air and water.

Actions

Multiattack. The dragon makes three attacks: one with its bite and two with its claws.
Bite. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 17 (2d10 + 6) piercing damage.
Claw. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 13 (2d6 + 6) slashing damage.
Breath Weapons (Recharge 5–6). The dragon uses one of the following breath weapons.
Fire Breath. The dragon exhales fire in a 30-foot cone. Each creature in that area must make a DC 17 Dexterity saving throw, taking 55 (10d10) fire damage on a failed save, or half as much damage on a successful one.
Weakening Breath. The dragon exhales gas in a 30-foot cone. Each creature in that area must succeed on a DC 17 Strength saving throw or have disadvantage on Strength-based attack rolls, Strength checks, and Strength saving throws for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.