Sucellus was created as the God of Nature and Growth. His Symbol was a Deer. He is considered a good god, but rarely if ever involved himself in the conflict with any rival in the Age of Dragons. He mostly kept to himself, and to a group of humans who were dear to him. His divine presence changed these men, making them fairer and longer lived. Although still able to interbreed with other men, they came to be seen as a seperate species: The Elves.
Sucellus's Archangel was Cernunnos, the Great Horned One, the Lord of the Forests, who is often considered to have been the strongest of all the angels, except for the Original 21. While Sucellus was not involved in the fighting, Cernunnos was much more aggressive. He alone dared to attack Agares himself in his deepest hell of Nyx. The huge Archangel was easily picked up like a rag doll in the hand of Agares, and shown visions of himself dark and corrupted. These visions shattered his psyche, and split him in two. The Dark version came to life, and was equal to him in size, strength, and shape, but evil and the color of blood. They did battle with each other, but neither could vanquish his foe. Cernunnos left Nyx, having gained nothing. Agares had gained the dark Cernunnos, whom he named Hyborem, as his archangel. Once Bhall and her angels fell, he became lord of the Balors.
... Mulcarn entered creation and with a whisper the Luchuirp army was wiped out. A permanent winter set in across creation.
The gods considered this breaking of the compact. They were unwilling to restart the Godswar, but couldn't let Mulcarn move into creation unchallenged. They agreed to let one god go into creation to fight Mulcarn. That god was Sucellus, the god of nature.
Sucellus entered creation and battled with Mulcarn. At the same time the Ljosalfar turned on themselves. They had agreed to shared power between two queens, one to rule during summer and the other during winter. The winter queen claimed dominance for years as winter showed no signs of ending and refused to give up the throne. This argument created a civil war and the new branch loyal to the winter queen called themselves the Svartalfar.
Sucellus lost the battle and was killed by Mulcarn. His body was broken in 7 pieces and scattered across Erebus. The Soul of Sucellus departed for the Underworld, where he helped Arawn, God of Life and Death, deal with the huge influx of souls that perished in the cataclysms that marked the beginning of the Age of Ice.
Creation froze even further and the elves were forced to stop their civil war as they could no longer mobilize armies or travel. They tried to find hidden places in the world to remain, and waited for the winter to end to continue their war...Facing first the brutal civil war and then the endless winter, life was extremely harsh on the Ljosalfar. It is unlikely that they would have survived, had not Cernunnos intervened. The greatest of the Archangels dwelt among them during this age, sheltering them as best as he could.
Once Mulcarn was vanquished, the seven pieces of the Sucellus' broken body were brought together in his tomb. Sucellus begged Arawn to let his return to life. To do this, he needed the Power of Life to be returned to creation. He also argued that this power wa necessary if creation was to recover from the long winter. This was originally the Precept of Nemed, who had gifted it to Arawn when he chose to renounce his godhood and father the human race. Arawn abhorred the abuse of Life and (especially) Death magic that had occurred in the Age of Magic, and had sworn to himself never to return to creation, lest he again be used as a conduit that allowed dark sorcerers to create such abominations. He remained adamant in this resolve, and would not return with Sucellus no matter how much he was cajoled. He was convinced, however, to gift the Precept of Life to his fellow god, just as Nemed had to him. Sucellus took this precept and was resurrected, now as the God of Life. This fundamentally changed his personality, and he came to be seen by his fellow gods as a new Nemed, whom all the gods held in high regard. All the gods are honored to have him in their presence, and he alone among the good or neutral gods is welcomed as a guest even by Agares into Nyx itself, without warfare.
The changes in Sucellus were profound, as a god personality is the very embodiment of his precept. The resurrected Sucellus felt he could no longer fulfill his role as god of Nature (for Nature requires a balance of Life and Death, and his new preference for Life would have thrown the natural world out of equilibrium), and so he gifted his old precept to his first and greatest creation. Cernunnos left the Ljosalfar and ascended into the Vault of Nature as a god. Once the Greatest of the Archangels, he is now the weakest of the gods, for he alone was not made by the hand of The One.
The symbol of Sucellus is now the Phoenix. The civilization representing his sphere is the Mercurians, but their leader (Basium, Arawn's Archangel of Life, who wanted the Precept of Life for himself so he could use it to fight demons)despises Sucellus.
Sucellus is stilled revered by the Fellowship of the Leaves, and his Priests (Druids) are the greatest healers the world has ever seen, being able even to resurrect the dead. He is the god of this age, the Age of Rebirth.