Invasion always go well with the word "Wrath". And seeing that there is no other word that could actually fit, we can first eliminate all other options and narrow it down to "Kael's Wrath" and "Wrath of Kael".
Both options sounds fishy, no?
Eh, not really. "Kael's Wrath" sounds more fishy because it denounces that the Wrath is owned by Kael. So it doesn't correlate with the Blood Elves. So, "Wrath of Kael" becomes your best choice!
If not, you can just call it "Siege of Kael and his group of angry and bloodthirsty transvestites to a human castle with an underleveled protection"