Why do newly born/created dark eldar need the suffering of others?

Why do newly born/created Dark Eldar need the suffering of others? They were not present during the birth of slaanesh, so they shouldn't have the void created in their souls like the eldar who were around in that time.

Dealing with the Warp, eldritch Chaos deities, and psychic residue isn't an exact science (or maybe even a science at all), but basically Slaanesh cursed the entire Eldar race from that point forward, irrevocably tainting them down the generations.

That's why all Craftworld Eldar need their spirit stones.

If the entire eldar race is cursed, how do the exodites deal with it? Do they also have spirit stones?

They are linked with the spirit of their maiden worlds.

Thanks for clearing that up for me, I honestly didn't expect anyone to respond to my questions.

No problem

Dark Eldar also experience an increase in the amount of suffering they need as time goes on, so I would extrapolate this backwards and say that newly-minted or newly born Dark Eldar probably don't feel much of a soul-hunger, and as they mature and age, it increases. Not that this is any real use to them, as they can't stay as children forever. But as to why they experience the need to feed on agony, I think daxxglaxx got it right - the very existence of Slaanesh is enough to cause soul-drain in a Dark Eldar. Slaanesh was created by the Eldar and is now inextricably linked to them as a race.

Craftworlders use a spiritstone and the protection of the Eldar Path to avoid attracting the attention of Slaanesh. Without the Path, they can devolve (or evolve, depending on your perspective) into Dark Eldar; in fact just about any Eldar could become a Dark Eldar, which is further evidence of Slaanesh's grip on the whole race.

Exodites, handily, cope with this by living too far from the Eye of Terror to be initially affected, and by maintaining a very non-Slaanesh-attracting life of hard work and simple living. The World Spirits are their Infinity Matrices and they also use spiritstones while alive.

Also, the birth of Slaanesh isn't an event fixed in Time. If Realspace is what we call spacetime, it's an event that originates outside of spacetime and stabs through it. The immediate cause of the event was the depravity of the eldar, who were bound to a point in time and space, but the event and Slaanesh itself exist outside of time and space, so it doesn't make sense to speak of 'before', 'during', and 'after' when referring to them. It would be as if you slashed a painting and the people inside the painting wanted to find you somewhere within. The slash is there, so you must be in there somewhere, right? But no, you're outside the painting.

And more, the Warp (or Immaterium) seems to be a platonic hyper-dimension where ideal essences originate and manifest, so entities like Slaanesh not only transcend Space and Time, but also Mind. So in one sense, it happened a long time ago, but in another very real sense, it's always happening right now, so naturally it would affect any eldar regardless of whether they were born then or now.

Actually, the event would even affect the eldar before it happened (as 'before' makes no more difference than 'after'), possibly causing their behaviour in order to create itself.

Really like the painting analogy. :-)

It's an interesting idea. Is there any fluff which directly supports it?

Well, we know that time doesn't truly exist in the Warp, given the general lack of physics, and the resultant time-travel-y shenanigans that ensue. Therefore, logically, beings entirely from the Warp must essentially be timeless, other than when they interact with reality. They're on an entirely different level of existance, they don't follow our rules until they impose them upon themselves.