The base game comes with 3 different bonus features. You can get random mystery symbols added to the reels at random times, and these will transform to reveal the same matching symbols. You can also land fully stacked multiplier wilds that cover reels 2 to 5, and the multiplier value will range from 2x to 10x.
Landing more than one multiplier wild means that the respective multiplier values will be multiplied with each other for potentially massive wins. The third and final base game feature gives you 1 to 3 scatter symbols, which might help you trigger the bonus round.
You need at least 3 bank vault scatters anywhere to trigger said free spins round, but landing more scatters than the minimum of 3 can lead to solid payouts. You win 20x, 200x and 2,000x your stake when you land 4, 5 or 6 scatters, respectively, and then you get to choose between 3 different bonus round options.
The Mystery Symbols option gives you 8 free spins, and a symbol will be randomly chosen at the start of the feature to serve as the sticky mystery symbol. When you land this symbol on reels 2 to 6, they will get a mystery sticker slapped on them and transform into a randomly chosen symbol. They will then reveal matching symbols on each spin, and covering a whole reel with mystery stickers gives you 1 extra spin.
The Expanding Wilds option gives you 10 free spins, and you will benefit from expanding wilds on the 2 middle reels. You get a respin for every expanding wild you land, and if you win on the respin the wild multiplier is increased by +1. This gives you another respin, and the process goes on as long as you keep winning.
The Multiplier Collect option gives you 12 free spins. You will collect coconuts above reels 2 to 5 here, and this increases the multiplier displayed above each reel. It takes 2 coconuts to increase the multiplier by +1, and this lights up 1 of 3 bars on the meter. You get 3 extra spins when all 3 lights on a reel's meter is lit. Whenever you land a regular wild, it will be upgraded with the multiplier value achieved on the relevant reels.