Great, that's just what I was hoping for. Thanks.
(Now the Angels of Death in my version will be skilled as serving both purposes the Dullahan were designed for. They'll have Life II for Destroy Undead and immortals they kill won't be coming back. Too bad base FfH doesn't have postCombat calls for promotions like FF. Getting the Netherblade to bind souls to the Netherworld will be a bit trickier. I can easily prevent actual Immortals from being reborn, but all those units who get immortality from blood of the Phoenix will be trickier. It still won't be as hard as trying to rewrite Resurrection to give an option of what unit to bring back and making the Netherblade prevent that ressurection though I suppose.)
Oh, I just noticed there were a couple of less important related questions I left off. (Actually I wrote them but tried posting between unplugging the Ethernet cable and logging on to the wireless network, so the post was lost and I had to try again.)
Does the immortal promotion really just count towards the immortal count, or it is handled differently? Would reducing the immortal count prevent a unit with the immortal promotion from being reborn just as easily as those intrinsically immortal? Does removing the immortal promotion from a unit without killing it reduce it immortal count?
Are the immortal points reset each turn, or can they carry over? (If I were to make my version of Consume soul use caster.changeImmortal(1) instead of adding the immortal promotion, would that mean only immortality for the one turn or would it let them store up multiple immoralities for use later?)
Oh, also may I assume that if rebirth is handled after Combat won that onUnitKilled is too, so I could give the dying unit a promotion like Golem to prevent it from returning as an Angel or Mane?