Ancient Copper Dragon

A copper dragon on the party's side is rarely a contract and never an obligation. She helps because she finds the party amusing, because the villain insulted her sense of humor, or because she has decided this campaign is the best show in three centuries. Play her as a generous patron with a cruel sense of timing: she will save the cleric's life and then mock his prayer for an hour.

In combat, she opens with Slowing Breath aimed past the party at the enemy line, since her cone is 90 feet and her allies have wisely stayed out of it. Acid Breath comes out only when she has a clean line and the party has called for it, because she does not love splash damage on friends. Rend goes on whichever enemy was loudest. Mind Spike (level 5, at-will via Spellcasting) chases a fleeing caster across the battlefield and marks them so she always knows where they are.

Out of combat she is the most useful and the most exhausting NPC in the campaign. Project Image lets her run an entire diplomatic scene from her cave. Greater Restoration once per day saves a PC from a fate worse than death, but she will charge the saving in a story she tells at every dinner for a year. Major Image creates the dragon the villain expects to fight while the real one Shapechanges past the gate as a maid.

She leaves on her own schedule, never the party's. When she goes, she leaves a riddle, a small magical item the party did not know they needed, and a standing invitation to come tell her how it ended.

Write her catchphrase before the session. She will say it three times, and the players will quote it for the rest of the campaign.

An ancient copper dragon is a trickster god of a small mountain. She has been there for centuries, she has watched a dozen kingdoms rise and fall from the same ridge, and the fight only starts because the party gave her a reason that finally bored her into action. Open the encounter on her terms: she has used Shapechange (at-will) to walk among the party as a Common-speaking bard, beggar, or rival adventurer for the last in-game day, and she knows exactly which PC to humiliate first.

When she drops the disguise, lead with Slowing Breath in a 90-foot cone, DC 22 Con. Failed saves halve speed, deny reactions, and force the choice between action or bonus action. That single breath neuters a paladin's smite-plus-attack rhythm and locks down the rogue's bonus-action Cunning Action. Save Acid Breath (14d8 in a 90-foot line, DC 22 Dex, 63 average) for the next round when clustered targets try to close. Multiattack gives three Rends at +15 for 28 average each, and she can replace one with breath or with a Mind Spike cast that ignores half cover and marks the target for her next round.

Legendary actions are where she enjoys herself. Giggling Magic on the cleric, DC 21 Cha, deals 31 psychic and forces them to subtract 1d8 from every attack and check until end of next turn, which usually breaks a clutch heal. Pounce gives her 20 ft. of movement plus a free Rend whenever the wizard tries to back away. Mind Jolt is a second Mind Spike if the breath is still recharging.

Four Legendary Resistances (five in lair) carry her through Banishment, Hold Monster, and Polymorph. Once Bloodied with no breath available, she Shapechanges mid-flight into a sparrow and laughs from a tree branch a hundred feet up. The party will not catch her. They will, however, owe her a riddle.

Have her ask one question before the first attack. The party's answer is the encounter's tone for the next four rounds.