Gargantuan undead, neutral

Armor Class: 21 (natural armor)

Hit Points: 396 (22d20 + 154)

Speed: 40 ft , fly: 79 ft , swim: 40 ft , climb: 39 ft

STR

28 +9

DEX

16 +3

CON

24 +7

INT

18 +4

WIS

18 +4

CHA

18 +4

Saving Throws: DEX (+8), CON (+14), WIS (+10), CHA (+11)

Damage Vulnerabilities: Fire

Damage Resistances: Necrotic

Damage Immunities: Poison

Condition Immunities: Charmed, Frightened, Incapacitated, Poisoned

Senses:

• Blindsight. 60ft.
• Darkvision. 120ft.
• Keen Sight and Smell. The Ancient Flood Dragon has advantage on Wisdom (Perception) checks used to find things using sight or smell.
• Passive Perception: 27

Languages: understands the languages it knew in life but can't speak

Challenge Rating: 22

Actions

• Multiattack. The Ancient Flood Dragon can use its Frightful Presence. It then makes three attacks; one Bite attack and two Claw attacks.
• Bite. Melee Weapon Attack: +15 to hit, reach 15ft., one target. Hit: 29 (4d10 + 5) piercing damage. The target must make a DC 22 Constitution saving throw or suffer the effects of the Flood Infection.
• Claw. Melee Weapon Attack: +15 to hit, reach 10ft., one target. Hit: 22 (4d6 + 6) slashing damage.
• Tail Shot. Ranged Weapon Attack: +15 to hit, range 20/90, one target. Hit: 17 (2d10 + 5) piercing damage.
• Frightful Presence. Each creature of the Ancient Flood Dragon's choice that is within 120ft. of it and aware of it must succeed on a DC 19 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the save at the end of each of its subsequent turns, ending the effect on itself on a success. If a creature saves successfully or the effect ends for it, the creature is immune to this feature for 24hrs.
• Infectious Breath (Recharge 5-6). The Ancient Flood Dragon exhales a cloud of infectious Flood spores in a 90ft. cone. Each creature in that area must make a DC 26 Constitution saving throw or suffer the effects of the Flood Infection.

Legendary Actions

The Ancient Flood Dragon can only 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 Ancient Flood Dragon regains spent legendary actions at the start of its turn.

• Detect. The Ancient Flood Dragon makes a Wisdom (Perception) check.
• Tail Attack. The Ancient Flood Dragon makes a Tail attack.
• Wing Attack. The Ancient Flood Dragon beats its wings. Each creature within 15ft. of the Ancient Flood Dragon must succeed on a DC 23 Dexterity saving throw or take 15 (2d8 + 5) bludgeoning damage and be knocked prone. The Ancient Flood Dragon can then fly up to half of its flying speed.