Ancient Tome Dragon

Innate Spellcasting. The dragon's innate spellcasting ability is Intelligence (spell save DC 25, +17 to hit with spell attacks). It can innately cast the following Spells, requiring no material components:

at will: Magic Missile, Hold Person, Chromatic Orb, Ice Knife, Invisibility, Web, Counterspell, Shield

3/day: Fireball, Sickening Radiance, Hypnotic Pattern, Raulothim's Psychic Lance

2/day: Steel Wind Strike, Wall of Force, Synaptic Static

1/day: Disintegrate, Forcecage, Globe of Invulnerability, Maze

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

Magic Resistance. The dragon has advantage on saving throws against spells and other magical effects.

Master of Words (Recharges on a Short or Long Rest). If the dragon would be reduced to 0 hit points, its current hit point total instead resets to 250 hit points, it recharges its Breath Weapon, and it regains any expended uses of Legendary Resistance. Additionally, the dragon can now use the options in the “Mythic Actions” section as well as it's Erudite Presence for 1 hour. Award a party an additional 62,000 XP (124,000 XP total) for defeating the dragon after its Master of Words activates.

Paper Scales. The scales of the dragon are covered in magical writings, similar to a wizard's spellbook. This allows the dragon to cast any spell of 5th level or lower as a ritual spell, but the spell can't have a duration of over an hour. The dragon uses it sparingly, since that takes away from its study or research.

Multiattack. The dragon can use its Frightful Presence or Erudite Presence. It then makes three attacks: one with its bite and two with its claws. Then it can cast a spell, depending on the number of attacks that it hit (one-at will spell, two-3/day spell, three-2/day spell)

Bite. Melee Weapon Attack: +10 to hit, reach 15 ft., one target. Hit: 8 (1d10 + 3) piercing damage plus 3 (1d6) force damage.

Claw. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 6 (1d6 + 3) slashing damage.

Tail. Melee Weapon Attack: +10 to hit, reach 20 ft., one target. Hit: 7 (1d8 + 3) bludgeoning damage.

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 25 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.

Primordial Breath (Recharge 5–6). The dragon exhales a small bead of raw primordial power which then explodes. It chooses a spot with 90 feet of it, and the attack covers a radius of 30-feet from that point. Each creature in that area must make a DC 25 Dexterity saving throw, taking 56 (16d6) (16d6) bludgeoning, cold, fire, or thunder damage (choice of the dragon) on a failed save, or half as much damage on a successful one.

Mythic: Erudite 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 25 Intelligence saving throw or become marked for 1 minute.

A marked creature has a -5 to attack rolls against the dragon, the dragon has a +5 to attack rolls against a marked creature, and it gains +5 to saves against any spell a marked creature uses. Additionally, it knows what spell a marked creature is using as well as the level they use it at.

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 Erudite Presence for the next 24 hours.

Studious Nature. The dragon spends the time studying a creature. The next attack it makes in the next minute against the target is made with advantage. If the attack hits, it deals an extra 5 damage.

Rewrite Story. The dragon can target one creature within 120 feet of it that succeeded on a saving throw that allowed it to avoid any effects since the end of the dragon's last turn. The target has to make the same saving throw with advantage or suffer the effects, even if the conditions are no longer the same.

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.

Mana Burst (Costs 2 Actions). The dragon explodes with raw mana. Each creature within 15 feet of the dragon must succeed on a DC 25 Dexterity saving throw or take 17 (2d6 + 10) force damage and be knocked prone. The dragon can then fly up to half its flying speed.

If the dragon's Master of Words trait has activated in the last hour, it can use the options below as legendary actions.

Mythic: Unending Knowledge. The dragon makes a claw attack and casts magic missile. The spell is cast at a level equal to the number of times it has hit with a claw attack since the start of its last turn (minimum of one).

Mythic: Words of Omnipotence (Costs 2 Actions). Words burst from the dragon's scales in a 90 foot cone. All creatures in the area must make a DC 25 Wisdom saving throw or be affected by one of the following. The dragon can choose a different affect for each creature.

-The target is effected mimicking a reverse gravity spell until the end of their next turn. It only affects the target and only 50 feet high.
-The target is blinded, and can make another save at the end of each of their turns.
-The target takes 5d10 force damage.
-The condition mimics the slow spell until the end of their turn.

Mythic: Pinnacle of Curiosity (1/day, Costs 2 Actions). The dragon casts Foresight and flies up to its speed without provoking attacks of opportunity.