Cold damage dealt by the void dragon ignores resistance to cold damage, but not cold immunity.

When the void dragon is killed it explodes in a swath of celestial destruction. Each creature and object within 1 mile of the dragon take 55 (10d10) bludgeoning damage, 55 (10d10) cold damage, and 55 (10d10) psychic damage. Each damage type can be reduced by half with a successful DC 21 saving throw: Dexterity vs. bludgeoning, Constitution vs. cold, and Wisdom vs. psychic. Additionally, a creature that fails two or three of the saving throws is affected by a plane shift spell and sent to a random plane. If it is sent to the plane it currently occupies, it appears 5d100 miles away in a random direction.

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

the region containing a legendary void dragon’s lair is warped by the dragon’s magic, which creates one or more of the following effects:

• Secrets have a way of coming to light within 6 miles of the lair. Clues are inadvertently discovered, slips of the tongue hint at a hidden truth, and creatures become morbidly curious for forbidden knowledge.

• Light is muted within 6 miles of the lair. Nonmagical illumination, including sunlight, can’t create bright light in this area.

• Visitations from otherworldly beings occur and disembodied voices whisper in the night within 6 miles of the dragon’s lair. Celestials, fey, and fiends of CR 2 or lower can slip into the world in this area.

if the dragon dies, these effects fade over the course of 1d10 days.

on initiative count 20 (losing initiative ties), the dragon takes a lair action to generate one of the following effects; the dragon can’t use the same effect two rounds in a row:

• The dragon negates natural gravity within its lair (an area affected by its gravitic breath is unaffected). Creatures drift 10 feet away from the ground over the course of a round and are restrained. Flying creatures can move at half speed, unless they have the (hover) tag or use magical flight, in which case they move normally. This effect persists until initiative count 20 on the following round.

• The Void briefly overlaps the dragon’s lair in a 20-foot-radius sphere of blackness punctuated by deep blue streaks and pinpoints of light. The sphere is centered on a point the dragon can see within 120 feet of the dragon. The area spreads around corners, is heavily obscured, and contains no air (creatures must hold their breath). Each creature in the sphere when it appears must make a DC 15 Constitution saving throw, taking 10 (3d6) cold damage on a failed save or half as much on a successful one. Any creature that ends its turn in the sphere takes 10 (3d6) cold damage. The sphere lasts until the dragon uses this lair action again or until the dragon dies.

• The dragon rips the fabric of space, forcing two creatures it can see within 120 feet of it to suddenly exist in the same place. Space itself repels the creatures to their original positions. Each creature takes 16 (3d10) force damage and is knocked prone, or takes half as much damage and is not knocked prone with a successful DC 15 Strength saving throw.

Void dragons dwell in the empty expanse between the stars, and do not require air, food, drink, or sleep. When flying between stars the void dragon magically glides on solar winds, making the immense journey through the void in an impossibly short time.