Optimizing Custom Dragon for a one-shot

[Ciel]

A couple of friends (6) and me are going to be doing this stupid level 20 one-shot, and so I was thinking about letting them fight an Ancient Red Dragon.
I don't think they would have a problem fighting it, so I was thinking about doing something wacky, like giving it Magic items and 2 Epic boons.

I ended up thinking about Brooch of Shielding with the Boons: Boon of Magic Resistance and Boon of Recovery.
Or giving it some other magic item like an insignia of claws and one of the Boons previously mentioned and Boon of Spell Mastery for the same protecting from Magic missile (shield spell) as the Brooch and getting that sweet bonus +5 ac, losing one of the other boons in the process. Also I was thinking about using the Shadow Dragon template.


What do you guys think? Too strong, too weak? Anything wacky I can add to it?

[solidork]

If I were going to use magic items to make 6 level 20s vs a dragon an interesting fight I'd go with: Horn of Valhalla, Iron (say your dragon has learned the ways of mortal combat, so they can use it), Ring of Invisibility, Wand of Polymorph, Ghost Step Tatoo and a bunch of various potions - then give a legendary action that lets them take the "Use a Magic Item" action.

[J-H]

Those are just defensive and won't do anything except extend the battle a bit by making it ignore a few spells. Against 6 players, you need some action advantages and action economy.

Give its bite a "Pass the Athletics check on hit or be grabbed, shaken, and thrown 50' for falling damage" rider.
Give it some spellcasting, including at least a cantrip as a Legendary Action. Blade Ward might be a good choice for a cantrip.
Give it minions or summons. Elementals are fine and easy, and maybe it actually has a bracelet with several Stones of Elemental Summoning.
Make the environment dynamic: Include moving pillars of earth, pools of lava, clouds of poisonous gases, or something similar. Maybe it has kobold minions who prepared traps?
Against 6 players, buff his HP and AC a bit.

[ImproperJustice]

At level 20?

Maybe make it radioactive and emit an EM jamming field that dampens or interferes with magic some.
Deals radiant damage with a potential sickened / poison rider.


Let it be some kinda crazy star dragon and give it some crazy star cultists.

Maybe a Space ship with an orbital death laser.

Some crazy nonsense to keep level 20s engaged. :)

[Unoriginal]

I would give the Red Dragon a Frostbrand Greatsword of appropriate size, as well ss a Multiattack using said greatsword.

I think it would be very cool to have the boss reveal they're not only an ancient dragon, but also a swordsmaster. Plus people who fight Red Dragons are rarely prepared for the cold or for a large mass of sharp metal moving very fast.

[Tawmis]

A mad wizard has tinkered around with the genetics of a Hydra and a Red Dragon trying to create their own version of Tiamat...

And in doing so, has successfully created a 5 headed, Ancient Red Dragon - that has the combined powers of both an Ancient Red Dragon and a Hydra.

So now the party isn't avoiding just ONE blast of fire - but five.

Not only that - you get:
Reactive Heads. For each head the Red Dragon Hydra has beyond one, it gets an extra reaction that can be used only for opportunity attacks.

Wakeful. While the Red Dragon Hydra sleeps, at least one of its heads is awake.

Multiple Heads. The Red Dragon Hydra has five heads. While it has more than one head, the Red Dragon Hydra has advantage on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.

Whenever the Red Dragon Hydra takes 100 or more damage in a single turn, one of its heads dies. If all its heads die, the Red Hydra Dragon dies.

At the end of its turn, it grows two heads for each of its heads that died since its last turn, unless it has taken ice damage since its last turn. The Red Dragon Hydra regains 10 hit points for each head regrown in this way.

Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.

Multiattack. The dragon can use its Frightful Presence. It then makes up to five attacks.

Bite.

Claw.

Tail.

Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 21 Wisdom saving throw or become frightened 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. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.

Fire Breath (Recharge 3–6). The dragon exhales fire in a 90-foot cone. Each creature in that area must make a DC 24 Dexterity saving throw, taking 91 (26d6) fire damage on a failed save, or half as much damage on a successful one.

Legendary Actions
The dragon can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The dragon regains spent legendary actions at the start of its turn.

Detect. The dragon makes a Wisdom (Perception) check.

Tail Attack. The dragon makes a tail attack.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 15 feet of the dragon must succeed on a DC 25 Dexterity saving throw or take 17 (2d6 + 10) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.

[J-H]

I would give the Red Dragon a Frostbrand Greatsword of appropriate size, as well ss a Multiattack using said greatsword.

I think it would be very cool to have the boss reveal they're not only an ancient dragon, but also a swordsmaster. Plus people who fight Red Dragons are rarely prepared for the cold or for a large mass of sharp metal moving very fast.

This sounds like fun. I like it.