Maybe he can't die in your version, but I know
I managed to kill him in AoI
Taranis's 'Pedia Entry said:
Mulcarn exemplifies many aspects of creation, one of these is Stasis. This is what he used to create his first servant, Taranis, called Taranis the Unchanging by men. His power is a gift and a curse; he will never be anything more or less than what he was at the moment of his creation. He cannot learn, he cannot adapt, he cannot grow, but neither can he be destroyed.
Mulcarn tasked Taranis with his protection, and as long as Taranis was close to his lord there was no power that could push him aside or destroy him. This is what Sucellus had before him when he came to fight Mulcarn.
Sucellus was the more powerful, but he could not injure Taranis. Likewise Taranis could not injure a god, but he could hold him off for eternity. They fought over the frozen wastes around Letum Frigis, neither making headway. Until Sucellus led Taranis to an island in the center of a frozen lake. Once there the God of Nature used his power to protect a small area from the touch of the blizzards that ravaged the land. The lake melted and Taranis was trapped on the island.
Sucellus went on to fight Mulcarn, and was killed by him. But Taranis still lives on that island, staring at the orb that keeps him trapped from across the deep lake he could never escape.
What is special about Taranis is that as an embodiment of stasis he can not change. I tend to think that perhaps he actually can be destroyed, but this destruction must be so great that it destroys all of him at once. Any injuries leading up to death are changes that cannot happen to him, but he can still be banished from Erebus.
All angels and demons seem to be immortal, not really in the true sense like Nemed and Os-Gabella, but in that when they are defeated their souls return to their god's vault to heal. The human(/elven/orkish/aifon) soul(/divine spark) is similarly immortal, but the mortal flesh lacks this immortality and will not regenerate to allow the soul to return to life. (Hmmm....I wonder if Taranis's inability to change would prevent him from being able to heal even in Mulcarn's vault. Of course, it might also mean he is the only archangel who would need no time for healing before leaving the vault again, as he was never injured, just moved.) The Divine Spark (which grants the possessor free will and the ability to channel mana) comes originally from The One. It is beyond the power of the lesser gods to create a divine spark, but one divine spark can give birth to another in the possessor's children. Mortal's inherited their mortality though a soulless mortal mother created by the combined action of the gods, but gained their immortal divine sparks from their father Nemed. (Although the pedia entries seem to say that Os-Gabella was created by the gods, her clear ability to use magic and her immortality of the same nature as Nemed's seem to me to indicate that she definitely has a divine spark and is beyond the gods' ability to create. Thus I am of the opinion that when the God of Life Nemed gave up his precept he split himself into two distinct and equal beings of either gender, so Os-Gabella is as much Nemed as the human Nemed is.) (I also tend to think that the Dwarven creation myth is just a myth and that they are in fact just another group descended from Nemed, since the idea that they have no souls seems wrong and racist. Originally in Kael's D&D games they were unable to use magic and had to hire human enchanters because of lacking divine sparks, but in FfH they can use magic. More importantly, they have religion and have specifically been shown pledging to give their souls to a god.)
We don't really have a lot of info on how the archangels were created. Kael has stated that they like the gods represent their spheres and so have personalities strongly connected to them, but that they are a "more human" representation of the sphere (although Mulcarn seems remarkably more human than Taranis). The One gave all his angels a Divine Spark that grants them free agency, but their precepts overwhelm their free will and force them to always think and act in terms of their one aspect. Erebus and Humanity was created so that divine sparks could dwell in a form made of equal parts of every aspect and thus be perfectly free to choose between them. (Even Agares was in favor of this and he is envious of the true "freedom of purpose" this affords humanity. He claims to offer those who fall with him freedom of purpose instead of just the illusionary freedom of action The One gave them, but I am of the opinion that freedom of purpose is impossible so long as they continue to control a precept and that only Nemed has attained such freedom. I believe that The One tried to take back the power of creation specifically so that the angels would give up their precepts and gain full freedom he had intended for them, but all the gods, even the good ones, have continued to use the power Agares stole and thus denied themselves the very freedom that they think they are fighting for.)
Satyr 'Pedia: Beltane Cycle said:
...Cernunnos lost his connection with Sucellus when he left the forest. But he hadn't realized that he could feel the connection with each of the gods until it was taken from him. Passionate Bhall, loving Sirona, vigilant Junil all had some part in his soul and drove him from the forest to save his son...
Recent pedia entries (like the Beltane Cycle) seem to imply that archangels have souls connected to multiple spheres and thus possessing free agency just like humans do. Obviously their god's sphere is dominant, but that is true even of humans who are devoted to their gods.
I typically guess that the angels(/demons), including archangels, were created by the gods using by splitting off a portion of their own souls into their new "children" (if so, I'm open to the dwarves having souls of the same sort as Kilmorph's angels and their creation story being true), perhaps in the same way as I guess Gabella was created only less evenly and where the god didn't give up his precept. Sometimes I wonder if maybe in doing so they might loose some of that aspect in themselves, so by making Taranis so fully embody Stasis Mulcarn made himself more prone to the changes of taking over creation, being slain, becoming a mortal, and becoming a god again. Kael however doesn't really support that view though, just holding that the archangels embody the same sphere but have the free will to embody it differently.
I've also toyed with the unorthodox view that maybe the gods didn't actually create their angels, and the distinction between Greater Angels/Demons (those who were always such) and Lesser Angels/Demons (former mortals) actually doesn't exist. In this view, the gods couldn't actually create any servants with divine sparks to be angels but they could adopt humans of the first generation (maybe even children of Nemed and Gabella before she rebelled?) and imbue them with their power. I find it interesting that Sucellus refers to the archangel not as Taranis the Unchanging but as Taranis
the Defiled. Defiled implies that there was some point before he was touched by some taint (to the god of gradual change/growth/maturation the curse of stasis is a serious defilement), which doesn't fit the the view that he was always unchanging. This would fit better with the idea that he existed first as a more mutable being who became eternally unchanging when made into a servant of Mulcarn.
