B'wana Beast is hidden on an island on the east side of the beach. You can reach him by making the little starfish pop up from the ocean. It takes a complete day and night cycle for the next starfish to appear, so you'll either have to wait or go to the hotel to skip to the next full day.
When you defeat B'wana Beast, you'll get the Multiverse version, which is probably one of the last figures you'll have to collect. Good luck!
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