Trying to bring about Armageddon isn't the defining quality of evil. While some evil civs want to destroy the world, most just want to corrupt and control it. Auric is firmly in this camp.
The Evil gods are those who opposed The One, siding instead with Agares. Agares did not think it was fair for The One to take away the power of creation which he had given them, and 6 of the 21 gods agreed. He offered them freedom of purpose instead of just freedom of action, which for an avatar of a precept means the freedom to corrupt the very nature of the precept.
Agares and the evil gods want 2 things: Freedom and Power. They think they should be free to use their power as they wish, but actually their power will always enslave them and attempting to use power in a way other than that The One intended will warp the power into something horrible. True free will is not possible to one is totally dominated by a single precept. In my view, The One has always intended his creations to have true free will, and he tried to remove the power of creation so that this free will would not be so hindered. I think any god could gain free will, but to do so must abandon his precept. Only one god has ever been willing to do this: Nemed, who gave up the precept of life in order to father humanity. He is revered by all the gods because of this, and the gods also now revere Sucellus because they see Nemed in him now that he has taken on the precept of life. Even Agares greatly admires Nemed for being willing to sacrifice so much to create something so great as Humanity. He also likes humanity, as he sees in it the same spirit of rebellion that spurred him on.
When The One discovered the corruption of Agares, it had already spread to all parts of Creation, including to the gods themselves. The One could not destroy the taint without destroying everything that had been tainted, which was everything. His holiness was so great that his mere presence would cause the destruction of the world he so loved, so he had no real choice but to withdraw to the True Heaven. However, before cutting Creation off, he tasked 7 gods still loyal to him with protecting humanity from evil and guiding it to enlightenment, so that one day the taint might be removed and he could rejoin his beloved creations. (The other 7 gods were still loyal to him too, but their precepts were ones that dealt more with preserving the natural world instead of humanity. The difference between good and neutral is largely contrived, but roughly corresponds to different levels of fanaticism and idealism versus isolationism and pragmatism.) The good gods (who had themselves been tainted, but not enough to rebel) too this command as a mandate to fight to destroy all evil, even though The One had never told them to try to destroy evil, just to protect good. (I think that he, like Jesus, would have ordered them to "resist not evil," as a fanatical devotion to destroying evil can drive us to do evil.) They built large armies of angels and beasts to aid in this crusade, and the neutral gods did the same to protect their own areas. In order to do so, all the gods relied on the power from the gems of creation which Agares had stolen; they don't seem to have minded the hypocrisy of using the stolen power of creation to fight those whose sin was stealing and using the power of creation. Agares constantly brings up this hypocrisy, and is disgusted by it.
Since Agares fell, his precept of Hope has been corrupted and changed into the precept of Despair. Just as he appears to forever grow old an wither, I think that his precept continually falls and drives him deeper into depression. While he was certainly active in the godswar, I tend to think that Agares has since then sunk deeper and become almost useless except as a figurehead for the movement. He once dared to hope that he could conquer the True Heaven and seize the throne of The One, but has always known deep down that this is beyond all hope. He destroyed his own paradisaical world of Nyx in spite, just as The One had chosen not to destroy his creation. Agares has since resolved to prove that The One is no better than him, that all his own shortcomings are but bad design on the part of The One or a vice in the omnipotent himself. While Agares may like to destroy Creation out of spite, he really wants The One to be the one to destroy it. The satisfaction of breaking The One's heart and showing him to be as flawed as his creations is the only victory left for him.
Agares and Ceridwen want to destroy Creation, but there is no evidence that the other evil gods share this goal. I tend to think that every god desires Creation succumb to his own precept. For Agares this means total despair, for Ceridwen it means ripping it apart, for Aeron it would be the total domination of the weak by the strong, for Camulos it would be chaos and war, for Mammon it would be greed and insanity, for Esus it would be the total loss of all truth, and for Mulcarn it would have been stasis. All of these are major deviations from the plan of The One, but they do not all equal Armageddon. Most of the evil gods would rather the world stick around for them to dominate.
Mulcarn was the least evil of the evil gods. His hell was unpleasant, but livable. He seemed to recognize that his aspect was but one of many important parts of The One's plan, that rest and winter were gifts that were needed in order to refresh and prepare for spring. I tend to think that he wouldn't even have sided with Agares had he not felt so abandoned by everyone else. He saw everyone moving on without him and grew very jealous of the worship given to all his siblings. This jealousy and sadness drew him closer to the greed of Mammon and the despair of Agares, while the burning passion of his nemesis Bhall (at the time the greatest champion of good) pushed him away from the side of good and his dislike for Sucellus drove him from the neutrals. Primarily though, his aspect is one that idealizes and wants to return to "the good old days", which in this case meant that he opposed the change of having the power of creation taken from him.
I tend to think that Auric is much more evil than Mulcarn was, which is tragic since he was such a nice boy. He bears a deep malice for Sucellus and Kyorlin for opposing him, and has extended this to all who seek to follow them. The reactionary drive to regain what was lost was always a bit darker than his usual aspect of keeping things as they are, and having lost godhood makes this element of his psyche dominant. Additionally, I tend to think that his human nature is trying very hard to balance out the strength of the element of ice in him, and is doing so through rapid fluctuations between elements of passion and despair, causing him to become very unstable and bipolar. He is seeking to do precisely the opposite of what Nemed did (which I personally consider to be The One's intent for his children), and so is further from his original purpose now than before his death. He feels a need to suppress his humanity in order to become a god again, and so is now less humane than before he was human.
