Mid-power Naya Polymorph!

Gameplan:

Atla needs three things to run smoothly, protection, a sacrifice outlet and the mana to cast her, ideally, you'd keep a hand with all three, but some card filtering and tutoring will probably be necessary.
When you cast Atla, you always want to have protection held up. Waiting until you have 5 mana and holding a Snakeskin Veil or Blacksmith's Skill is infinitely better than playing her immediately and having her removed.

One or two egg flips should be enough to win you the game, since all the creatures in the deck are game-ending threats, with the exception of Mirror Entity.

Notable Inclusions:

The reason Mirror Entity is included is because you can either sacrifice it immediately to get a threat, as it is all creature types, including egg, or you can use it as protection on a bigger board, making your other creatures all creature types if they're about to die, effectively replacing themselves. Activating it for 1 mana in response to a boardwipe has absolutely saved games.

Porphyry Nodes is another spicy pick, you can either use it as removal, to pick off small creatures, or make an egg in response to the upkeep trigger and use it as a sacrifice outlet. It provides great value for just one mana.