It could be a -1 from Jace, the Mind Sculptor, it could be a Ravenous Chupacabra, it could just a be a Doom Blade
It's just a little bit more of a glass cannon that I would expect but then again, that sort of makes sense in a deck based around 50/50 chances of winning
If you play something like Elves, Goblins, Humans, or Merfolk, you can fill your deck with 30 creatures of the right type and never worry about your mana curve because these creatures exist at all reasonable points in the curve, but if you ever play 30 Giants in a deck, then the average converted mana cost will be five and you will lose most games without ever casting a spell
Welcome to Commander, Magic's most popular multiplayer format
Or you can slot Zurzoth into the 99 of Nekusar, the Mindrazer or similar