Like every other house, planet and sign, the symbolism of the 8th House has both positive and negative possible implications. And, also like every other house, planet, and sign – the way you figure out whether to use a positive or negative implication is to figure out if the specific combination in question is mostly positive or negative.
A few examples will make it more clear how to do this.
Sun in the 8th house tends towards negative implications, because the Sun is a very visible planet, but the 8th is a very mysterious, secretive house. So there is lack of synergy – which causes interpretations to favor the negative permutations. So, we read the Sun in the 8th as a signal of poor vision, lack of leadership skill, lack of career success, and poor health.
Nonetheless, even though the Sun in the 8th is normally negative, we still must consider the sign of the 8th house, as well as the overall dignity the Sun has through the vargas. For example, if the 8th house is Aries or Leo, we have to include some positive spin on the interpretations – and if the overall varga dignity is also significantly above average we might shy away from negative implications all together. Thus, the Sun in the 8th house Aries, with great dignity throughout the aṁśa-varga would read like this: “Ability to see what others cannot (instead of “poor vision”), ability to share democratic power (instead of “poor leadership”), career success in a niche and/or in partnership with others (instead of “poor career”), and strong overall health.
So, whether or not things turn out bright or dark depends on the exact situation, and is very difficult to exhaustively document because there are so many possible “exact situations.”
The very basic starting points for various planets in the 8th house (gleaned from a study of the expected results described by texts like Brhat Parasara Hora, and Phaladeepika), shows that the 8th house is no exception to the general principle that the benefic planets generate good results wherever they go, and the malefic planets generate bad results. Starting from this general principle, examine how the sign influences the planet, and the planet’s overall dignity and then you can reach a conclusion.
This consideration should also inform your interpretation of the lordship yogas.
For example, let’s take two extreme situations in the 8th house: One with Saturn in Aries with terrible overall dignity, and the other with Jupiter in Cancer with great overall dignity.
In this example, Saturn would be the lord of houses 5 and 6. One thing expected when Saturn is in the 8th is the restriction (♄) of reproduction (8). This will surely become a very important theme when Saturn is also the 5th house lord, because that is the house of children. So, a very important interpretation to make here is one pointing towards no children, or dramatic problems with them. Saturn in the 6th also indicates weakness (♄) in the life-force (8). This is particularly important when Saturn is the 6th lord, because the 6th is the house of illness. So another very prominent interpretation of Saturn in Aries, the 8th house, with terrible overall dignity, is very, very bad health.
Now, in the other example, Jupiter in Cancer with great overall dignity, Jupiter would be lord of the 1st and 4th houses. Jupiter in Cancer begins by suggesting just the opposite of what Saturn suggested here: longevity and fertile reproduction. With Jupiter as the lord of the 1st (concerning health) we should surely consider it a very strong indication of very positive health and very long life. Jupiter on it’s own represents children, so fertile reproduction is also an important reading here. Jupiter as the 4th lord indicates that we would have enduring (8th house) happiness (4th house), deep (8) emotions (4), and shared (8) property (4) that can endure (8) through any challenges. In short, because Jupiter is (a) benefic, (b) exalted and (c) in excellent overall dignity, therefore we interpret the 4th lord in the 8th house bringing out only the positive possibilities of the symbolic combinations.
Should we have a 4th lord in the house as (a) a malefic, (b) in a difficult sign for it, and (c) in very bad overall dignity, then we should do just the opposite with our interpretation: bring out only the negative possibilities.