Soul EggsYou gain Soul Eggs by prestiging or completing certain Missions. Each Soul Egg gives a permanent 10% boost to your income, or more with the Soul Food Epic Upgrade (see below). It is recommended to first prestige when you have over fifty Soul Eggs for your first prestige, giving a 500% (×6) boost. After that, there are different strategies, but a general rule of thumb is at first to prestige when you can get double your soul eggs, when the number of soul eggs you will get is equal to your current number of soul eggs. You will then restart to the Edible Egg farm, keeping only your Pro Permit, Epic Upgrades, Missions or Trophies, Piggy Bank, Soul Eggs, and Prophecy Eggs.
When you prestige, you gain (prestige bonus)*(cash/1000000)^0.15 soul eggs on earlier eggs. On later eggs, the exponent is higher, e.g. on the Antimatter Egg the number of eggs you get is roughly (prestige bonus)*(cash/1000000)^0.173525.
Soul Food, an Epic Upgrade, strengthens the ability of Soul Eggs. Each level adds a 1% boost to all Soul Eggs (i.e. a level 4 would have a 14% boost). Soul Food has 140 levels, with a maximum of 150% bonus to egg value.
Prestige Bonus, an Epic Upgrade, gives more Soul Eggs per Prestige. Each level adds 10% more Soul Eggs at restart (i.e. a level 5 would have 50% more Soul Eggs than normal (i.e. 15,000 rather than 10,000)). Prestige Bonus has twenty levels, with a maximum of 200% bonus soul eggs when prestiging.