Every 10 levels, you will unlock a new upgrade. These can be bought with Dark Cookies, and simply boost common things such as loot bags, daily gifts, cupcakes and more.
Every 100 levels get a 5x dark cookie production boost! This can be very useful for players hit a wall around novemvigintillion cookies!
Levels 101-200 get a bakery boost and rare candies upgrade!
Levels 201-300 get a Rainbow Storm boost and Enchanted cookies!
Levels 301-400 get a Gold & Platinum and Milk Crate!
Level 401-500+ get 3 Cupcake Upgrades!