Thank you all for your lines. Jordi (Kul's owner) has no account in this forum, but I'll report him your kind commentaries.
So, is there a rule in play to keep Kul alive for a bit at least? As is, he is pretty much the biggest cannon target in the history of warhammer.
Jajajaja! Yeah... maybe we will have tu put a line of giats and other monsters in front of him!
Well, more seriously, he has similar stats with Archaon, which includes and special guard save of 4+ o 3+... don't remember exactly. On the other hand, empire artillery will have more importants targets to shoot, specially, winged monsters and flying units.
No special rule for that Illumini.
I understand you are talking about the death of Asavar Kul descibed in some books... but there is also another -most epic- version of his death. It appears in an ancient White Dwarf (about when GW released Hordes of Chaos army book) and explains the youth of this Chosen One and how he conquered leadership of his tribe (the Kurgan). In this version, it was Magnus the Pious himself who defeated Asavar Kul in a duel. Much more epic... but also much more unreal. Magnus was a priest with high leadership skills, and some kind of fighting skills... but obviously, very far from any chosen of Chaos, not talk in comparison of Asavar Kul itself.
Didn't Magnus defeated Kul in every version of this story? I've only read two, I think - in one the dying Kul says something about his Gods forsaking him, while Magnus delivers the most badass line, about Sigmar always being by his side. It reads much better in the original, so just take my word on that. 
There is a version where Asavar Kul is killed by his back when storming the walls of Kislev, just at the turn of the tide, by some unkown chaos warrior.
