Void Dragon

Void Dragon earns $120M/s, the second-best of the wiki's six Event-rarity pets after Ember Dragon ($600M/s). It ranks 8th of 17 event pets and 67th of 198 overall.

Mutations have to be applied before it hatches

For a pet you cannot farm from a nest, the wiki documents two consumables that can add a mutation outside the hatch roll. Both work on an egg sitting in your pen, not on a hatched pet:

• Mutation Shard (Rift Boss Shop, paid in Boss Tokens): 10% chance to apply Fractured, ×2.75. The wiki says it works on growing and fully grown eggs.
• Scrambled Mutation (Dr. Scramble's Experiment Shop, 475 Samples): 10% chance to apply Scrambled, also ×2.75.

On Void Dragon either one would mean about $330M/s, if you still have its egg in the pen. Once the pet is out, the wiki documents no way to add a mutation.

Origin

The wiki lists Void Dragon as an event pet without naming the event, the date or how it was distributed. Its general note on limited eggs says that event eggs never appear in biome nests and come only from the Store or from special events such as Admin Abuse. Despite the name, nothing on the wiki ties it to the Rift's Void Angler, Voidmaw or Void Serpent.

Comparable pets

• El Maja, the Eternal of the Abyss Ocean biome: $130M/s, egg grows 5h 30m, reward +180k Speed and $13b.
• Strawberry Elephant, Brainrot Egg: $110M/s.

Estimates

The wiki lists a base weight of 12,000 kg. With its documented formula:

• Golden: about $300M/s
• Rainbow: about $420M/s
• 10× weight: about $496M/s
• 100× weight: about $2.05B/s
• 200× weight: about $2.84B/s
• Rainbow at 100× weight: about $7.19B/s