Warhammer 40k fluff thread VI: They see me Ward'en, they haten

[Cheesegear]

How big of a threat are the Dark Eldar? Are they a 'local' threat, in that they're only pirates and are unlikely to do serious damage to any of the other factions?

They are a threat anywhere there is a webway gate.

If so, then although their numbers are very low with respect to the other major factions, they are disproportionately dangerous for their numbers.

Yes and No. Because of their low numbers, they generally don't cause massive damage like other factions. But, they're fast and they don't stick around after they've finished what they're doing (capturing people). Furthermore, because they live in the Webway, they're basically impossible to catch once they're gone.