If you’re one of the users of ancient blue dragon 5e then you can get the all of the below mentioned features such as Traits, actions, legendary actions, also the attributes. All of them will be discussed below.

Traits

Legendary Resistance (3/Day): The ancient dragon of the blue can fail a saving throw and choose to make another attempt.

Actions

Multiattack: The ancient blue dragon is able to use its Frightful Presence in this multiattack. It then uses its bite to attack one and its claws to attack the other two.

Take a bite: The bite attack can be used by the monster to create a Melee weapon attack. It is +16 to hit, reach 15, ft. and one target. Also Hit: 20 (2d10 + 9) piercing damage plus 11 (2d10) lightning damage.

ClawUsing the claw, the dnd old blue dragon can create Melee Weapon Attack. +16 to hit, reach 10 feet., one target. Hit: 16 (2d6 + 9) slashing damage.

Tail: Melee weapon attack: +16 to hit. Hit 20ft. one target. Hit: 18 (2d8 + 9), bludgeoning.

Frightful Presence: Each and every creature of a blue Dragon 5e choice that is within 120 feet must succeed on the DC 20 Wisdom saving Throw or it should be frightened for a moment. If a creature is able make another saving throw at each turn, it will also be able end its effect on the creature on that particular success. Suppose, if the creature’s saving throw is being successful or else the effect would be end for it and then the creature is immune for the  dragon’s Frightful Presence for the next 24 hours.

Lightning Breath (Recharge 5-6)Basically, the d&d5e ancient blue dragon can exhale lightning in a 120-foot long line measuring 10 feet wide.  Each creature in the line should make a DC 23 dexterity saving throw.

Learn more about giant ape 5e monster

Legendary Actions

You can select from these options to make the 5e old blue dragon perform three legendary actions according to the dungeons & dragons monsters. Basically, the only one legendary action can be used simultaneously, and of course it should only be at the end of  an another creature’s turn. The legendary Actions that you have spent are redeemed at the beginning of each turn.

Detect: The Wisdom (Perception), check is made by the d&d old blue dragon.

Tail Attack: A tail Attack is made by the d&d ancient dragon.

Wing Attack (Costs two Actions): The d&d old blue dragon is naturally able to beat it wings. Every creature within 15ft. of a dragon must succeed on a DC 24 Decterity saving throw, or it should take 16 (2d6+9) bludgeoning damages and be knocked out. Even though the ancient dragon in d&d is able to fly at half its normal speed,

Attributes Of DnD 5E Ancient Blue Dragon

AC 22 (Natural Armor).
Alignment Lawful Evil
CHA 21
CON 27
Challenge Rating 23
DEX 10
HP 481 (26d20+208).
INT 18
Immunities Lightning
Languages Draconic and Common
Passive Perception 27
Roll 0 Take 1d20 and 16 2d10+9+2d10
Roll 1 Claw 1d20 + 16 3d6+9
Roll 2 Tail 1d20 + 162d8+9
Roll 3 Lightning Breath 1d20 + 0 16d10
STR 29
Throws that Save Dex +7; Con +15; Wis +10; Cha +12
Senses Blindsight 60 feet, Darkvision 120 feet
Size Gargantuan
Skills Stealth +7, Perception +17
Speed 40 ft. Burrow 40 ft. Fly 80 ft.
Type Dragon
WIS 17