In Dota 2, there are numerous rare couriers that are a source of pride for their owners. Among the rarest ones, we can highlight:
Golden Baby Roshan - awarded to the top players during Diretide 2012. See how it looks: https://www.youtube.com/watch?v=EOy-ADwRj-Q Platinum Baby Roshan - similar to the golden version, the platinum Baby Roshan was the reward for top players in Diretide 2013. Its visual appearance is shown in this video: https://www.youtube.com/watch?v=3_6WteLdg-A Desert Sands Baby Roshan - awarded to top players in Siltbreaker mode. More about it in the video: https://www.youtube.com/watch?v=0DI39rR1GbI Dark Moon Baby Roshan - an extremely rare reward in the Dark Moon event. Here's what it looks like: https://www.youtube.com/watch?v=mX9Efl-3Cg4 All of these couriers were available during limited-time events, and only a very small number were released. Prices for them reach thousands of dollars.
FAQ ENSI 
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Golden Baby Roshan - awarded to the top players during Diretide 2012. See how it looks: https://www.youtube.com/watch?v=EOy-ADwRj-Q
Platinum Baby Roshan - similar to the golden version, the platinum Baby Roshan was the reward for top players in Diretide 2013. Its visual appearance is shown in this video: https://www.youtube.com/watch?v=3_6WteLdg-A
Desert Sands Baby Roshan - awarded to top players in Siltbreaker mode. More about it in the video: https://www.youtube.com/watch?v=0DI39rR1GbI
Dark Moon Baby Roshan - an extremely rare reward in the Dark Moon event. Here's what it looks like: https://www.youtube.com/watch?v=mX9Efl-3Cg4
All of these couriers were available during limited-time events, and only a very small number were released. Prices for them reach thousands of dollars.