They resemble stones with a purple five-faceted jewel set inside.
The information below implies that Soul Beacons do not work, but Soul Beacons appear to work, implying that the information below is inaccurate.
The Soul Eggs you earn when prestiging are calculated based off of your total prestige earnings, via the following formula.
epic_soul_egg_prestige_bonus*(prestige_earnings/1,000,000).15 epic_soul_egg_prestige_bonus*prestige_earnings.15/7.94 (after rounding)
Your prestige earnings can be found under Stats.
There are a few ways to increase the potency of Soul Eggs.
Soul Food Edit
Soul Food, an Epic Upgrade, strengthens the ability of Soul Eggs. Each level adds a 1% boost to all Soul Eggs (e.g. a level 4 would have a 14% boost). Soul Food has 140 levels, with a maximum of 150% bonus to egg value per Soul Egg.
Eggs of Prophecy Edit
You can increase the potency of soul eggs by 5% (compounding) with Eggs of Prophecy. Each Prophecy Egg increases the potency of all soul eggs by 5-10%, depending on your level of Prophecy Bonus, an Epic Upgrade.