Elder Deep-Fiend is an Eldrazi Octopus that can be normally cast for eight generic mana, or cast with its Emerge cost (for an overview on how Emerge works, please refer to TechRaptor's Monday article)
How can someone convince you of anything when you know what your deck can do, your weakness, and your threat
It does get better with commander tax as you can employ similar strategies that overlap with aristocrat commander Prossh, Skyraider of Kher and abuse all those tokens you make from the powerful cast trigger
Im excited to see that trend continue
It's also a key component of infinite mana combos in Commander, where it converts an arbitrary stack of mana into lethal damage
Then during combat, it deals 2 damage to Caged Zombie again, which only now deals its own damage