Large Dragon (Metallic), Lawful Good
Traits
Amphibious. The dragon can breathe air and water.
Actions
Multiattack. The dragon makes three Rend attacks. It can replace one attack with a use of Weakening Breath.
Rend. Melee Attack Roll: +10, reach 10 ft. Hit: 17 (2d10 + 6) Slashing damage.
Fire Breath (Recharge 5–6). Dexterity Saving Throw: DC 17, each creature in a 30-foot Cone. Failure: 55 (10d10) Fire damage. Success: Half damage.
Weakening Breath. Strength Saving Throw: DC 17, each creature that isn't currently affected by this breath in a 30-foot Cone. Failure: The target has Disadvantage on Strength-based D20 Tests and subtracts 3 (1d6) from its damage rolls. It repeats the save at the end of each of its turns, ending the effect on itself on a success. After 1 minute, it succeeds automatically.
Found on p.144 of MM2025 (Free Rules)