Small dragon, any alignment (usually good)
Armor Class 10
Hit Points 21 (6d6 + 0)
Speed 0 ft.
Saving Throws Int +13, Wis +12, Cha +13
Skills Arcana +13, History +13, Perception +12, Religion +13
Damage Vulnerabilities bludgeoning, cold
Damage Resistances fire, lightning, slashing
Damage Immunities acid, thunder, poison
Condition Immunities blinded, deafened, petrified, poisoned, restrained
Senses blindsight 60 ft. (blind beyond this radius), passive Perception 20
Languages understands Common and Draconic, but can't speak, telepathy 60 ft.
Challenge 15 (13,000 XP)
Glowing Gemstone. Due to an eldunarí being little more than a spherical gem-like object, it cannot make or succeed in Strength or Dexterity saving throws or checks. It can use legendary resistance to succeed in such saving throws.
Eldunarí cannot move without someone carrying them. They give off dim light in a 5-foot radius around themselves.
Legendary Resistance (3/Day). If the eldunarí fails a saving throw, it can choose to succeed instead.
Desperate Diversion. If a creature attempts to make an attack roll against or cast a spell on the eldunarí, the eldunarí may use its reaction to use Subtle Aversion against that cteature with DC 17.
Multiattack. The eldunarí makes three strain mind attacks.
Strain Mind. Ranged Spell Attack: +13 to hit, reach 60 ft., one creature. Hit: 13 (2d6 + 8) psychic damage. Standard AC does not affect this attack. An opponent's AC for this attack is 10 + its Intelligence modifier. If the opponent has defense against mind effects (such as charmed, but does not include resistance or immunity to psychic damage) or are able to use telepathy, they may add their proficiency bonus. Finally, AC bonuses from magic items still apply.
The eldunarí 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 eldunarí regains spent legendary actions at the start of its turn.
Sense Mind. The eldunarí may make a Wisdom (Perception) check to sense nearby creatures.
Subtle Aversion. Up to 2 creatures of the eldunarí's choice must make a DC 25 Intelligence saving throw or be unable to bring themselves to do anything harmful or detrimental to the eldunarí. This lasts until the eldunarí's next turn. (Harmful or detrimental include, but is not limited to, attacks, spells with negative effects, etc.)
Total Control (2 actions). The eldunarí chooses a creature. That creature make an Intelligence saving throw contested by the eldunarí's Intelligence check. If the eldunarí wins, they control that creature until the end of that creature's turn (if the creature has already finished its turn this round, then this effect lasts until the end of the creature's next turn).
Eldunarí appear can spherical gem-like object that glow with an inner light. They can have a diameter of 12 inches to 36 inches.
In rare cases, an ancient dragon nearing death may perform a ritual that creates an the gem-like object and transfers its consciouness into the object (the inner light corresponds to their former species, gold for a gold dragon, red for a red dragon, ect.). Their bodies usually die soon after. As eldunarí are unable to move on their own, this ritual is usually performed with a trusted friend or family member nearby. Being unable to move and nearly at the mercy of whoever is carrying discourages almost all evil dragons, and most good dragons as well, from even attempting to try to find the ritual, let alone perform it.