Ancient Silver Dragon

Legendary Resistance (4/Day, or 5/Day in Lair) If the dragon fails a saving throw, it can choose to succeed instead.

Multiattack The dragon makes three Rend attacks. It can replace one attack with a use of (A) Paralyzing Breath or (B) Spellcasting to cast Ice Knife (level 2 version).

Rend Melee Attack Roll: +17, reach 15 ft. Hit: 19 (2d8 + 10) Slashing damage plus 9 (2d8) Cold damage.

Cold Breath (Recharge 5-6) Constitution Saving Throw: DC 24, each creature in a 90-foot Cone.

Paralyzing Breath Constitution Saving Throw: DC 24, each creature in a 90-foot Cone. First

Spellcasting The dragon casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 23, +15 to hit with spell attacks):
At Will: Detect Magic, Hold Monster, Ice Knife (level 2 version), Shapechange (Beast or Humanoid form only, no Temporary Hit Points gained from the spell, and no Concentration or Temporary Hit Points required to maintain the spell)
1/Day Each: Control Weather, Ice Storm (level 7 version), Teleport, Zone of Truth

Preamble Legendary Action Uses: 3 (4 in Lair). Immediately after another creature's turn, the dragon can expend a use to take one of the following actions. The dragon regains all expended uses at the start of each of its turns.

Chill The dragon uses Spellcasting to cast Hold Monster. The dragon can't take this action again until the start of its next turn.

Cold Gale Dexterity Saving Throw: DC 23, each creature in a 60-foot-long, 10-foot-wide Line.

Pounce The dragon moves up to half its Speed, and it makes one Rend attack.