Adult Nickel Dragon

Magic Resistance. the adult nickel dragon has advantage on saving throws against spells and other magical effects.

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

Spellcasting. The adult nickel dragon is a 12th-level spellcaster. The adult nickel dragon's spellcasting ability is Intelligence (spell save DC 21, +13 to hit with spell attacks). It requires no material components to cast its spells. The adult nickel dragon has the following wizard spells prepared:

Cantrips (at will): friends, prestidigitation, shape water, control flames

1st level (4 slots): shield, magic missile, mage armor*, fog cloud

2nd level (3 slots): mirror image, misty step, invisibility, hold person

3rd level (3 slots): glyph of warding, counterspell, bestow curse, blink

4th level (3 slots): banishment, greater invisibility, dimension door, polymorph

5th level (2 slots): passwall, wall of stone, transmute rock, mislead

6th level (1 slots):disintegrate, globe of invulnerability, eyebite, contingency*

*The adult nickel dragon casts these spells on itself before combat.

Multiattack. The dragon can makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 15 (4d4 + 5) piercing damage.

Claw. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 11 (3d4 + 5) slashing damage.

Tail. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 11 (2d6 + 5) bludgeoning damage.

Theft (Recharge 5–6). The adult nickel dragon attempts to steal an ability or spell it has seen from a target within 20 feet of it. The target must make a DC 21 Charisma saving throw, on a failure the adult nickel dragon learns the targeted ability or spell for 24 hours.

Nullify (Recharge 6). The adult nickel dragon attempts to nullify an ability or spell it has seen from a target within 20 feet of it. Target must make a DC 21 Charisma saving throw, on a failure the targeted ability or spell is nullified and can not be used indefinitely or until the adult nickel dragon has died. This effect can be removed with Greater Restoration.

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.

Spellcasting. The adult nickel dragon casts a spell of 5th level or lower.

Tail Attack. The dragon makes a tail attack.

Scuttle (Costs 2 Actions). The adult nickel dragon moves up to its movement speed. This does not provoke opportunities of attack,