[SPOILER] Plot Discussion Thread *Spoiler Alert*

[Streetboat]

My interpretation of the 'egg' is a metaphor for the hatching of this alternate personality of Mandus'. He says he laid it right there with the bones of his children, by the rhododendrons, implying he was split when he buried his children, and his alternate personality was hatched at that moment.

Or, it could be another version of the Orb from the first Amnesia. I prefer the first explanation, though, the second is too 'deus ex machina'.