Adult Gold Dragon

An adult gold dragon on the party's side is a judge before it's a weapon. Golds are Lawful Good, fluent in Common, and proficient in Insight (+8) and Persuasion (+13). Before any fight, it will want to know exactly what the party is doing and why. Play the conversation first. If the party's cause is just, the dragon helps. If it isn't, the dragon either declines or proposes a different plan, and the party either accepts the correction or loses the ally on the spot.

Use Zone of Truth (1/Day) as a scene tool, not a combat one. The gold dragon will cast it on a captured prisoner, a suspect noble, or a doubted ally before it commits to violence on the party's behalf. This is the hook for involving it in mysteries and trials. The dragon will sit through a half-hour interrogation and consider the ten-minute Zone of Truth more useful than its breath weapon.

In combat the gold leads with Weakening Breath rather than Fire Breath when the party is fighting alongside it. The 60-foot cone, DC 21 Strength save, halves enemy damage and gives Disadvantage on Strength tests for up to a minute. That makes the party's frontline survivable against bigger threats. Save Fire Breath (12d10, DC 21 Dex, recharge 5-6) for the round you're allowed to clear a clustered group with no allies caught inside. Banish (legendary, DC 21 Cha) is the dragon's panic button for the party: when a PC is about to die, banish the attacker for a round so a healer can reach them.

The gold leaves the moment the cause is won. It will bless the party in formal Draconic, take flight, and be gone. Don't let players keep it as a flying mount for the rest of the adventure, because the moment it becomes a tool, it stops being a character.

Before the session, decide what the gold dragon's standing question is. "Why are you doing this?" or "Who profits if you succeed?" Ask it once, in character, and see who at the table can answer cleanly.

A hostile gold dragon is rare and almost always means the party is on the wrong side of something. Maybe they have been hired by an evil patron and the dragon knows it. Maybe they desecrated a temple it guards. Maybe they took a relic the dragon was sworn to protect. Sell the misunderstanding or the moral weight first, because a gold attacking the party should feel like the cosmos has rendered a verdict.

Open from the air. Fly speed is 80 ft. and the dragon hovers above effective melee range to lead with Fire Breath: 66 average fire damage, DC 21 Dex save, 60-foot cone. On recharge, alternate with Weakening Breath to neuter the party's striker before round two. The Multiattack swap lets the dragon trade one Rend for Guiding Bolt (level 2), which is your handing-out-Advantage tool: cast it on the rogue so the next ally to swing has Advantage, then watch the next legendary action capitalize.

Legendary actions are where the dragon dictates pace. Banish (DC 21 Cha) removes one PC from the fight for a round and deals 3d6 force; use it on whoever is best positioned to land a meaningful hit, ideally during their own turn so they lose actions. Pounce keeps the dragon mobile after a forced landing. Guiding Light is your repeatable ranged poke, especially good at extreme altitude.

Three Legendary Resistances (four in lair) mean save-or-suck spells will mostly fail. Telegraph this. The first time a wizard burns a 7th-level slot and the dragon shrugs, the party should understand the rules of the room. Once Bloodied without Fire Breath ready, the dragon offers a parley. It will name a price: a confession, a returned relic, a sworn oath. A gold dragon would rather see the party turn back than die.

If they accept the deal, end the fight cleanly and the gold becomes a recurring NPC who watches the party from a great distance for the rest of the campaign.