>>96438810
>>96429220
Name me a single eldar demon prince. The bulk of Slaneesh's as any chaos God's actual physical forces and worshippers are within the imperium. Even if you count the cock sword as xenos treachery it was still Fulgrim's choice to pick it up. You don't see any farseers going around to sacrifice 30000 souls to summon a keeper of secrets into the material realm and even the dark eldar try to keep themselves away from that stuff, though they do dabble in it from time to time. Ultimately Slaneesh would eventually run out of eldar souls to feast because most of them plainly don't worship her or go around chanting her battle cries in overcharged speaker systems
However Slaneesh does seem weirdly popular within xenos in a way the other chaos gods aren't which is interesting or might just be a coincidence