Steal an Egg Rift event: Overlords, Boss Tokens, Mastery, Sacrifices and the three banners

A Rift opens somewhere on the map every 30 minutes. You step inside, fight the Overlord waiting there, and if you defeat it you earn Boss Tokens. Tokens are spent in the Boss Shop. Every Overlord you beat also adds Boss Mastery Points, and the Mastery track unlocks rewards as you progress. That is the whole loop: find the rift, win, spend, repeat on the half-hour.

The Boss Shop sells temporary boosts — cash multipliers, speed multipliers and treadmill boosters — plus one item that is not temporary: a consumable Mutation Shard with a chance to apply a mutation to an egg already sitting in your pen. The wiki's FAQ on the page answers the obvious question: the shard works on both growing and fully grown eggs, and the chance of it working is 10 %.

Read together with the Mutations page, the shard is how Fractured gets onto an egg: the Mutations page lists Fractured (×2.75) as a mutation that cannot come from a normal hatch roll and can be applied to an egg with a Mutation Consumable for a 10 % chance, and the Update 3 notes say the Boss Shop offers 'a chance to apply the new Fractured Mutation to your placed eggs'. It is not the only after-the-fact mutation: the same Mutations page lists Scrambled (×2.75), applied from Dr. Scramble's Shop at 10 %, and Spirit Bloom and Bloom from the Sakura Incubator, which it marks as not currently active. So a shard is, in effect, a 10 % ticket to ×2.75 on whatever egg you point it at — which is why the best use is your highest-base egg, not your favourite.

Every Overlord defeated earns Boss Mastery Points, and progressing through the Mastery track unlocks increasingly valuable rewards, including eggs pre-loaded with the Fractured mutation. The wiki does not publish the track's thresholds or the full reward list, so this page does not either. What it does establish is that Mastery is a route to a Fractured egg that does not depend on the shard's 10 % roll.

Separate from the timed boss fights, the Rift Event page describes a Rift that sits permanently in the lobby. It asks for three random pets; hand them over and it grants one exclusive Rift Egg. The catch is which pets it asks for: the Sacrifice draws from whichever banner is currently active, and each banner's pool is split into three difficulty tiers by how demanding the pets are to obtain. The tiers are listed in full below. Rotation is roughly every three hours (Update 3 adds that rotations are globally synchronised across every server), and the event page's FAQ says pity carries over — it does not reset when you leave the game or when the banner changes.

The permanent Rift rotates through three egg pools. Each pool draws its pets from a set of biomes rather than a single zone.

This is the list to check before you commit pets. Easy-tier pets are cheap zone eggs; hard-tier pets are the ones you would rather keep.

Seventeen pets are tied to the Rift on the wiki: sixteen are filed under Rift in its pet data module, which drives the Rift Event page's pet gallery, and Void Dragon's infobox also says Rift while the module files it as an Event pet. The event page's headline says 18 new pets. Shattered Colossus has no filled infobox, so its rarity and income come from the module. They span Legendary to Divine. None has a listed grow time or hatch reward.

Three things follow from the rules. First, the sacrifice tiers make some cheap pets worth keeping: a Lava Gecko or Parrotfish is easy-tier on two banners, so they are the cheapest pets to keep for a Sacrifice. Second, because pity carries over across leaving and rotation, there is no reason to rush a banner you do not like. Third, the 30-minute rift cadence lines up with the five-minute nest reset six times over, so a normal steal-hatch routine fits between rifts without waste.

What the wiki does not tell you, and this page will not guess: how strong the Overlords are, what the Mastery thresholds are, exact Boss Shop prices, or how long the event runs. Its FAQ does describe one fight mechanic: the Overlord periodically faints during the encounter, and each hit on its hand with the bat then does 100 damage.

Several pets appear in the sacrifice lists of two banners, which makes them the most flexible pets to hold in a pen for the Rift. From the wiki's tier lists:

The seventeen Rift pets break down as one Divine (Shattered Colossus, from the pet data module), four Eternals (Void Serpent, Shattered Drake, World Eater, and Void Dragon by its infobox), four Secrets (Shardwing, Mawbreaker, Wendigo, Abyss Overlord), three Cosmics (Shattered Ram, Dreadclaw, Ventinal), three Mythics (Shardling, Riftwing, Voidmaw) and two Legendaries (Void Angler, Rift Eye). Nine of the seventeen are Secret or above, and twelve are Cosmic or above. A zone's eight nest eggs, by comparison, run from its cheap starters to one or two top eggs.

The rift cadence is 30 minutes and the nest cycle is five, so a session naturally splits into six-cycle blocks: steal and hatch on the nest timer, be at the rift on the half-hour, spend tokens, repeat. Because pity carries over across leaving and banner changes, there is no penalty for logging off between rifts, and no reason to force a banner whose tiers ask for pets you would rather keep. Wait roughly three hours for the rotation instead.

The wiki's Rift Event page carries a short FAQ. Does applying a Mutation Shard work on eggs that are still growing? Yes — it works on both growing and fully grown eggs in your pen, but there is only a 10 % chance of it working. Does pity reset when I leave or when the banner rotates? No — pity carries over regardless of leaving the game or the banner changing. How do you use the shard? Walk up to an egg in your pen and interact with it. Those answers are the strategic core of the event: shards are a slow-burn lottery best pointed at your biggest base, and pity means patience costs nothing.

The page headline lists 18 new pets, a Rift Boss Event, Boss Mastery and a new currency. The currency is the Boss Token (Update 3: 'Defeat it to earn Boss Tokens. Spend your Boss Tokens in the Boss Shop'); the event page's tip calls the batch you receive after each fight 'Boss Shards' and says to save them for the Boss Shop boost that fits your progression. The wiki ties seventeen pets to the Rift by their data, one short of the headline. Its Rift category has eighteen members at the 21 October 2026 read, but the eighteenth is Stag, whose infobox and data entry both give Cherry Blossom as its biome, so the category does not settle the count. None of them is a nest pet, which is why the zones page treats the Rift as an event rather than a thirteenth zone, and why the pets hub lists them without grow times: the wiki has none to give.

The wiki does not give an end date for the Rift Boss Event, and the Update 6 notes say the Rift Trade-In Machine has already been replaced by Dr. Scramble's Laboratory. If you want a Rift pet, fight the Overlord every 30 minutes while the event runs, and check the Updates page before you plan around the Sacrifice.