Legendary Resistance (3/Day). If the dragon fails a saving throw, it can choose to succeed instead.
Multiattack. The dragon can use its Frightful Presence. It then makes three attacks: One with its bite and two with its claws. Alternatively, each head can attack a different creature for three attacks total.
Bite. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 18 (2d10 + 7) piercing damage plus 5 (1d10) lightning damage.
Claw. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 14 (2d6 + 7) slashing damage.
Tail. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: 16 (2d8 + 7) bludgeoning damage.
Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 17 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.
Vampiric Breath (Recharge 1d4 rounds). The dragon exhales vampiric gas in a 30 ft cone. Each creature in the area must make a DC 19 Constitution saving throw, taking 33 (6d10) necrotic damage on a failed save or half on a successful save. In addition, any creature affected by the breath also has its total hit points reduced by half of the damage dealt. This effect lasts until the affected creature takes a long rest. The Dzalmus also gains hit points equal to half of the total damage dealt to all creatures per breath weapon use, up to its max.
The dragon can 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 dragon regains spent legendary actions at the start of its turn.
Detect. The dragon makes a Wisdom (Perception) check.
Tail Attack. The dragon makes a tail attack.
Fog Cloud. The dragon casts the Fog Cloud spell.
Pass Without Trace.
Lair and Lair Actions
Unlike younger Dzalmus dragons, Adult Dzalmus's will sometimes form permanent lairs. Often, these lairs can be found among the runes of ancient abandoned castles, temples, and other structures within the Endless Waste. The Dzalmus may extend the structure slightly further underground to help protect its treasure horde from thieves.
On initiative count 20 (losing initiative ties), the dragon takes a lair action to cause one of the following effects; the dragon can’t use the same effect two rounds in a row:
- Animate Dead. The Dzalmus is able to cast Animate Dead as a 5th level spell. The creatures raised are based on those that inhabited the area before the Dzalmus converted it into a lair.
- Sand Storm A cloud of sand swirls about in a 20-foot-radius sphere centered on a point the dragon can see within 120 feet of it. The cloud spreads around corners. Each creature in the cloud must succeed on a DC 15 Constitution saving throw or be blinded for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
- Cloudkill. The Dzalmus casts Cloudkill as a 5th level spell.
The region containing a legendary blue dragon’s lair is warped by the dragon’s magic, which creates one or more of the following effects:
- Undead creatures roam the land within 6 miles of the lair. For each hour spent within 6 miles of the lair, roll 1d6. On a 1, the party has a random encounter with 1d10 skeletons and 1d8 warhorse skeletons.
- Dust devils scour the land within 6 miles of the lair. A dust devil has the statistics of an air elemental, but it can’t fly, has a speed of 50 feet, and has an Intelligence and Charisma of 1 (−5).
- Hidden sinkholes form in and around the dragon’s lair. A sinkhole can be spotted from a safe distance with a successful DC 20 Wisdom (Perception) check. Otherwise, the first creature to step on the thin crust covering the sinkhole must succeed on a DC 15 Dexterity saving throw or fall 1d6 × 10 feet into the sinkhole.
If the dragon dies, the dust devils disappear immediately, and the undead wither away within 1d10 days. Any sinkholes remain where they are.