Steal An Egg: How to Get the Cosmic Skeleton Boss Egg and Spirit Bloom

The heaviest egg you can pull off in Roblox’s Steal An Egg is the Secret Cosmic Skeleton Boss Egg, a monster that tips the scales at 13,210,649 kg. It spawns in the Cosmic area, gets carried back to your safe zone like every other steal, and becomes a top-tier earner once you mutate it into its rare Spirit Bloom form before hatching.

Quick answer: Grab the Secret Cosmic Skeleton Boss Egg when it spawns in Cosmic, carry it into your safe zone, spend 1.5K Sakura Crystals plus Robux in the Cherry Blossom mutation chamber to roll the 2.5% Spirit Bloom, then hatch it for a pet that generates $14.2B/s base and $28.5B/s when active.

How to steal the Cosmic Skeleton Boss Egg

The egg only appears through a server-wide spawn. When the alert “A Secret Cosmic Skeleton Boss Egg spawned in Cosmic!” pops up, the egg is waiting in the Cosmic zone, guarded by the sleeping boss. Because it is the heaviest egg in the game, your avatar moves much slower while carrying it, so the run back is the hard part.

Head to the Cosmic area the moment the spawn notification appears. Speed matters here, so equip your fastest trail and keep your treadmill speed high before the round.

Player runs through the Cosmic Lake area toward a spawned Secret Cosmic Skeleton Boss Egg — Running through the Cosmic area toward the freshly spawned Secret Cosmic Skeleton Boss Egg. Image credit: Steal An Egg / via @codezzyrbx

Grab the egg from the boss. Expect to be knocked down at least once, and expect other players to chase you for the same steal.

Carry it slowly back through the zones and cross into your safe zone pen. Once it drops into your pen, the steal is locked in and no one can take it from you.

Egg spawns and the ALL EGG RESET

High-value eggs come from timed spawns tied to each zone. Alerts name the egg and its area, and multiple secrets can appear at once, letting you chain steals across Prehistoric, Volcano, and Abyss Ocean before the timer runs out.

Reaching the safe zone as three secret eggs spawn at once across different zones. Image credit: Steal An Egg / via @codezzyrbx

The “ALL EGG RESET!” event refreshes every egg spawn across the map at once. This is the fastest window to sweep several secret and eternal eggs in a single sprint, so line up your route from the icy Snow area through to Cosmic before the reset fires.

The ALL EGG RESET alert refreshes spawns across the whole map at once. Image credit: Steal An Egg / via @codezzyrbx

Mutate the Cosmic Skeleton Boss Egg into Spirit Bloom

Mutations happen in the Cherry Blossom area’s mutation chamber. You charge an egg with Sakura Crystals and Robux, then roll for an upgraded version. The Cosmic Skeleton Boss Egg becomes far more valuable as a Spirit Bloom, but that outcome is rare.

Mutation	Base chance
Bloom	97.5%
Spirit Bloom	2.5%

Take the stolen egg to the mutation chamber in the Cherry Blossom zone.

Deposit 1.5K Sakura Crystals to charge the egg, then add Robux to push the roll toward the rare result.

Confirm the mutation. You will see the message “Your Cosmic Skeleton Boss Egg is now Spirit Bloom!” when the rare version lands. Placing it in your garden then shows a growth time of about 1 day 6 hours.

Grow and hatch the egg

Once planted, the egg sits on a long growth timer before it can hatch. You can wait it out, or spend Robux to skip the timer and open everything in your garden at once. A full-garden instant grow ran 64 Robux.

Growing Eggs panel open with several egg rows and green OPEN buttons ready to select — The Growing Eggs panel, where finished eggs show green OPEN buttons ready to hatch. Image credit: Steal An Egg / via @codezzyrbx

When the Spirit Bloom Cosmic Skeleton Boss Egg hatches, it reveals a giant green skeleton pet. That reveal confirms the mutation and hatch both worked.

What the Spirit Bloom pet generates

The Spirit Bloom Cosmic Skeleton Boss produces $14.2B/s as its base rate and $28.5B/s when active, which is what makes the long mutation and hatch worthwhile. Equipping it alongside your other best pets can lift a total generation rate toward 125B/s, close to the leaderboard cutoff of 163.1B/s.

Pet	Income
Spirit Bloom Cosmic Skeleton Boss (active)	$28.5B/s
Spirit Bloom Cosmic Skeleton Boss (base)	$14.2B/s
Bloom Eternal Lunar Dragon	$466M/s
Bloom Stag	$318M/s
Legendary Salamander	$8M/s

Pet Index with Salamander selected, showing its Legendary income and claimed rewards — The Pet Index tracks each pet’s rarity and income, like the Legendary Salamander shown here. Image credit: Steal An Egg / via @codezzyrbx

Other large eggs worth stealing

The Cosmic Skeleton Boss Egg is the heaviest, but several other secret eggs are worth chasing during the same reset window. Weight rises with rarity, and heavier eggs slow your carry, so plan shorter routes for the biggest ones.

Egg	Weight
Cosmic Skeleton Boss Egg	13,210,649 kg
Prehistoric Egg	8,302,747 kg
Volcano Egg	1,763,548 kg

Eggs from the Cherry Blossom zone, like the Secret Stag Egg, can also be mutated to a Bloom version for a big income jump. A Bloom Stag lands at $318M/s and a Bloom Eternal Lunar Dragon at $466M/s, so it is worth routing through the Forest and other zones on the way to collect them.

Crossing the Forest course, one of the zones you run through while chasing spawned eggs. Image credit: Steal An Egg / via @codezzyrbx

There is no code redemption system in Steal An Egg right now, so free boosts have to come from normal play. Focus on hatching regularly, sweeping the ALL EGG RESET spawns, and mutating your best eggs before they hatch. You can jump into the game from its official Roblox page at roblox.com/games/107778070777162 and watch for future updates that could add new eggs, mutations, and events.