Random events shape almost everything you do in Build a Base and Steal. They decide when you farm cash, when you lock down and roll, and when you sneak into a rival plot while everyone else is distracted. As of the Build Mode Update, six events can appear on their own, each with its own timer and its own payoff.
Quick answer: An event has a chance to spawn every 30 minutes. The six events are Money Rain (4 min), Roll Rush (5 min), Zombie Invasion (5 min), Cosmic Invasion (5 min), Volcano (5 min), and Fishing (10 min). Money Rain and Roll Rush appear most often; Volcano and Fishing are the rarest.
Every event, effect, and duration
Here is what each event does and how long you have to act before it disappears.
| Event | What happens | Duration |
|---|---|---|
| Money Rain | Wads of Cash and Money Bags fall from the sky. A Wad of Cash pays your MPS; a Money Bag pays 10x your MPS. | 4 min |
| Roll Rush | Pet Rolls and Block Rolls wind up faster and have a higher chance of landing rare pets and blocks. | 5 min |
| Zombie Invasion | Zombies spawn across the map and attack players. Each kill grants 0.10 Luck toward a Luck Boost that applies when the event ends. | 5 min |
| Cosmic Invasion | UFOs abduct your pets and return them with the Cosmic Mutation. | 5 min |
| Volcano | Lava rains across the map and damages players. Pets hit by lava gain the Inferno Mutation, and a cage inside the volcano holds a free Inferno Pet. | 5 min |
| Fishing | A fishing area opens at the center of the map where you use a rod to catch fish pets. Stealing is turned off. | 10 min |
How events spawn and how often
The game checks for an event roughly every 30 minutes, and each event carries a different spawn chance. Money Rain and Roll Rush are the two you will see the most. Volcano and Fishing sit at the low end, so they only turn up occasionally.
All six events can also spawn in private servers, including Fishing and Volcano. That matters if you want the free Inferno Pet from the volcano without other players racing you to the cage.
Cash and rolling events: Money Rain and Roll Rush
Money Rain is a fast cash boost. Grabbing a Wad of Cash gives money equal to your MPS, and a Money Bag gives ten times that amount. It is strongest for new players who need quick funds for gear, pets, and blocks. Once your base is full of high-earning pets, the extra income barely moves the needle.
Roll Rush is the collector’s event. Both the Pet Roll and the Block Roll spin faster and lean toward higher rarities. Lock your base and spend the full five minutes rolling. The higher your main luck, the more this event returns, so don’t waste it on stealing or building.
Zombie Invasion: turn kills into a Luck Boost
Every zombie you kill during the event adds 0.10 Luck. Kill 10 zombies and you finish with a +1x Luck Boost that lasts for 10 minutes after the event ends. Zombies can walk into your base even when it is locked, so locking up mainly keeps your pets safe while you focus on hunting.
The smart play is to stack kills during the event, then spend the 10-minute Luck window hammering Rolls for the rarest pets and blocks. Zombie Invasion also doubles as cover for a raid, since other players are busy fighting. Just remember they can try the same trick on you.
Mutation events: Cosmic Invasion and Volcano
Two events change your pets instead of your wallet. Cosmic Invasion sends UFOs to abduct pets and return them with the Cosmic Mutation. Volcano rains lava that applies the Inferno Mutation to any pet it hits. For both, the plan is the same: put your best pets in the base so they pick up the mutation.
Both events feed permanent progress. Filling out the Cosmic Pet Index and the Inferno Pet Index each grant a permanent Luck and Cash Boost, so treat these events as index-completion time. During Volcano, you can also break the cage at the center to free and claim an Inferno Pet. Expect competition for it, which is another reason a private server helps.
Note: Volcano lava damages players, and Inferno pets are contested, so the event also works as a distraction for a quiet raid while rivals are busy at the cage.
Fishing: the only way to get fish pets
Fishing is the longest event at 10 minutes, and it is the sole source of fish pets. When it spawns, a fishing area opens at the center of the map and you receive a rod to start catching. Stealing is disabled for the whole event, so there is no reason to guard your base.
Spend the full 10 minutes fishing and improving your rod, since a better rod raises your odds of pulling rare fish pets. Because Fishing is one of the rarer events, take advantage of the full duration whenever it appears.
Read the event the moment it starts and commit to its single best action. Farm during Money Rain, roll during Roll Rush and after Zombie Invasion, stack your best pets for Cosmic Invasion and Volcano, and fish the whole window when Fishing shows up. Knowing the timer for each one is what separates a wasted event from a rare pet or a permanent boost.
