Armor Class 21
Hit Points 402 (23d20 + 161)
Speed 40 ft., fly 80 ft., swim 40 ft.
Saving Throws DEX +8, WIS +10
Skills Deception +13, Perception +17, Persuasion +13, Stealth +8
Damage Immunities poison
Condition Immunities poisoned
Senses Blindsight 60 ft., Darkvision 120 ft., passive Perception 27
Languages Common, Draconic
Challenge 22
Amphibious. The dragon can breathe air and water.
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 Spellcasting to cast Mind Spike (level 5 version).
Rend. m +15, reach 15 ft. Hit: 17 (2d8 + 8) Slashing damage plus 10 (3d6) Poison damage.
Poison Breath (Recharge 5–6). con DC 22, each creature in a 90-foot Cone. 77 (22d6) Poison damage. Half damage.
Mind Invasion. The dragon uses Spellcasting to cast Mind Spike (level 5 version).
Noxious Miasma. con DC 21, each creature in a 30-foot-radius Sphere centered on a point the dragon can see within 90 feet. 17 (5d6) Poison damage, and the target takes a -2 penalty to AC until the end of its next turn. The dragon can't take this action again until the start of its next turn.
Pounce. The dragon moves up to half its Speed, and it makes one Rend attack.
Monster Manual (2024), p. 154