Just spotted something the other day, that although Soulrazor can kill something outright, it isn't doing so via the "Instant Death" rule: Soulrazor special rule from the Diresword (codex Eldar p64) - Models that suffer 1 or more unsaved Wounds from this weapon must pass a Ld test for each unsaved wound or die.

Wheras the Eternal Warrior special rule in the BRB specifically, as written, protects against the "Instant Death" special rule.

Which one wins here? Can you one-hit kill something with multiple wounds remaining and Eternal Warrior (assuming that it fails the Ld test), with a wound from a Diresword?

Going as written, that Soulrazor doesn't use the Instant Death rule to do it's instant kill, that Eternal Warrior is useless. However, this seems to be against the intention of Eternal Warrior, and one likes to think that if Asurmen and a Dire Avenger Exarch get in a fight, that the Phoenix Lord's special rule ought to be taking precedent over that of his subordinate...