Ancient Spirit Dragon

If the dragon fails a saving throw, it can choose to succeed instead.

The dragon makes three Rend attacks. It can replace one attack with a use of (A) Time-Warping Breath or (B) Spellcasting to cast Thunderwave (level 2 version).

Melee Attack +15, reach 15 ft. 19 (🎲2d10 + 8) 🗡️ Slashing damage plus 9 (🎲2d8) 💀 Necrotic damage.

CON Save DC 22, each creature in a 90-foot Cone [Area Of Effect].
Failure: 72 (🎲16d8) 💀 Necrotic damage.
Success: Half damage.

WIS Save DC 22, each creature that isn't currently affected by this breath in a 90-foot Cone [Area Of Effect].
Failure: The target's Speed is halved, it can't take Reactions, and it can take either an action or a Bonus Action on its turn, not both. It repeats the save at the end of each of its turns, ending the effect on itself on a success. After 1 minute, it succeeds automatically.

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

The dragon uses Spellcasting to cast Thunderwave (level 2 version).

The dragon magically raises broken, ancient ruins in a 20-foot-radius, 60-foot-high Cylinder [Area Of Effect] centered on a point it can see within 120 feet. Ground in the Cylinder [Area Of Effect] becomes Difficult Terrain. Each creature in the Cylinder [Area Of Effect] when it appears is subjected to the following effect. STR Save DC 22.
Failure: 13 (🎲3d8) 🔨 Bludgeoning damage, and the target has the Prone condition.
Success or Failure: The dragon can't take this action again until the start of its next turn.