Adult Gold Dragon

If the monster fails a saving throw, it can choose to succeed instead.

The monster can breathe air and water.

The monster makes three Rend attacks. It can replace one attack with a use of (A) Spellcasting to cast Guiding Bolt (level 2 version) or (B) Weakening Breath.

Melee Attack: +14, reach 10 ft., one target. Hit: 15 (2d8+6) Slashing damage plus 4 (1d8) Fire damage.

Dexterity Saving Throw: DC 21, each creature in a 15-foot-long, 5-foot-wide Line. Failure: 66 (12d10) Fire damage. Success: Half damage.

The monster casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 21): At Will: Detect Magic, Guiding Bolt (level 2 version), Shapechange (Beast or Humanoid form only, no Temporary Hit Points gained from the spell, and no Concentration or Temporary Hit Points required to maintain the spell). 1/Day Each: Flame Strike, Zone of Truth.

Strength Saving Throw: DC 19, each creature that isn't currently affected by this breath in a 60-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.