Darkness" is a state without light. "Light" is truth from the Lord, so "darkness" represents a state where truth is lacking. Here's a cogent passage from Arcana Coelestia: "The person who has yet to be regenerated is called 'a void and an empty earth', and also 'ground', in which no good or truth at all has been sown - 'void' where there is no good, and 'empty' where there is no truth. Consequently there is 'thick darkness', or stupidity and lack of knowledge about anything that has to do with faith in the Lord and so anything that has to do with spiritual and celestial life. (Arcana Coelestia 17)

3829. 'Jacob said to Laban, Give me my wife' means that general good was now to be joined to the affection for interior truth. This is clear from the representation of 'Jacob' as the good of the natural, dealt with already, in this case general good because the things that constitute the natural are general in comparison with internal things. For countless things flow in from the internal man into the natural or external man where they manifest themselves as a general whole, the more so when the particular things that make up general wholes have not yet been received, as is the case here. This is why the good which 'Jacob' represents is now called general good. The joining of this good to the affection for interior truth is clearly meant, for Rachel, to whom 'my wife' refers here, represents the affection for interior truth, as shown above.