Currently spawns only occur based on stream-based events (follow, start streaming, etc.) There are many, many other cool events that could spawn items in the world such as:
nth follower milestones (10K in any claw member)
nth player that joined p4nth3rworld
nth item to spawn
any player reaches n wealth
any player reached n items
etc., you get the idea :)
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@matthewbrandt say more!