Due to aat'aat being so gigantic and hardy, they are capable of carrying unthinkable amounts of weight.

The equipment of you and any allies you are carrying does not count towards your carry weight limit. Your push and drag weight, and your lifting and carrying capacity in other situations uses your hit point maximum instead of your Strength.

The fortitude of aat'aat is legendary- your Constitution score and its maximum are raised to 30, and you gain an additional 1d4 hit points per level. In addition, you only need to rest for 4 hours to get the benefits of a long rest, and have advantage on all Constitution saving throws. While you require massive amounts of food and water, you only need to feed once a month.

Your thick fur coat offers great protection from most normal attacks- you have resistance to non-magical bludgeoning, slashing, and piercing damage, and your AC becomes set at 1d10+Constitution modifier. However, you also become vulnerable to Fire type damage, and in general are uncomfortable in high heat; you also are unable to wear any armor, due to your immense size and bulk.

Your massive size make it hard for you to be stopped, but you aren't very mobile.

You become unable to take the Dash or Disengage actions, but you gain the Endure action at level 7, which allows you to use your reaction to take Constitution modifier+proficiency less damage from non-magical attacks until the start of your next turn.

You're also immune to forced movement from Large or smaller creatures and objects, and non-magical difficult terrain doesn't slow your movement; you also have disadvantage on all Dexterity saving throws and ability checks.

Your bulk is imposing and can be quite disruptive, but you don't have much raw destructive power.

Your unarmed attacks use your Constitution instead of your Strength, and hits either knock the target prone or push it your speed. In addition, due to being a quadruped, you cannot grapple creatures, or wield weapons of any kind.

Your size also makes it difficult to hit smaller things- you have disadvantage on all unarmed attacks against Large or smaller creatures.

Although your biology prevents you from articulate speech, you are capable of understanding and even reading Common and one other language. Deep in your instincts is knowledge of Celestial, as well. You communicate through grunts and other vocalizations and gestures, which can make you understood, but gives you disadvantage on all Charisma ability checks.