The Morrigan of Terrath (Moor- eh - gahn)

The Morrigan of Terrath is a legendary (name pending she is, of course, loosely based on the Morrigan of our world. I say "loosely" because the Morrigan we know is a vague outline of the Irish/Celtic mythology that survived past the initial rise of Catholicism. What we do know about the Morrigan is collected knowledge of what survived. A lot of what survived was passed chiefly from word of mouth, this being especially important because after Christianity gained ground, many pagans were looked down upon. And in some eras, they were persecuted and killed. But all that's for a different discussion.
We know very little about the Morrigan or the Morrigna compared to other mythologies. There are speculations about her being one or three goddesses; one person I know believes that the Morrigan is more of a title given to fierce goddesses. But if you were to see her as one, then there are at least three noticeable aspects.
war, prophecy, and death
The Morrigan is heavily associated with war, and if she favors you or your side. Then you are likely to win the war. She challenges Cu Chulainn, a legend I will not get into for now.
One of her most interesting aspects is her association with fate and prophecy. It is the Morrigan who appears to the soldier and washes his bloody armor. It is the Morrigan who is said to foretell doom and the fall of kingdoms.
Then you have the association with death, albeit a minor one. She is married to the Dagda, the chief of all the Tuath de Danan. But her association with war and the crow tie her in with death itself.
Now to the Morrigan of Terrath
The Morrigan of Terrath is the first of the "human" based pantheon in Terrath (there's a pantheon of nature deities, and they are NOT human ), the reason why I opted to do a "human" based pantheon (I haven't decided if I'm gonna do a multi-species with intellectual creatures I could and I'm considering it but I haven't decided)
She is also the first Legendary (again, name pending) of Terrath. A legendary is one who the elder gods (nature) have deemed worthy of leading their kind forward. Each legendary aligns themselves with one of the 6th elders; She chose Visalth, the elder of the west and god of life and creation. While it was Visalths parents who created him, he in turn created man, and beast, and tree. She stood as his eternal guardian, the goddess of a merciful death, of war and strategy, and of wisdom.
She became the goddess of death because she understood the importance of the life and death cycle. Her grief for her lost family and her mistakes that have led good men and women to death taught her as much about the value of death as it did the beauty of life. In this wisdom, she asked that she be reborn when old kingdoms fall and new kingdoms rise. She also asks that she choose herself who is to be her host, to train them to bring forth the new era and take wisdom from the mistakes of the old.
When the Morrigan is ready to help prepare the loom of fate, she is known as the wise woman. She takes on the appearance of a humbled old hag. And searches for the warrior whose new ideas and new ways of thinking will bring on the next era. When wise woman and warrior exist separately, they are known as the Morrigna. The warrior can be chosen from any culture or race.
In her warrior form, she is known as the goddess of war. >.> She helps establish new kings and kingdoms, advises the courts on when diplomacy or war is necessary.
As wars fade, she becomes the goddess of wisdom, maintaining peace for as long as she can. This can be for a generation, or it can be for many. There is legend of one who had been captured and held for 1000 years. But when the kings no longer listen, when they become spoiled and tyrannical, is when she goes to become a wise woman.
And yes, I know what your thinking "wait, she's the wise woman during the times of peace, but her final stage is the wise woman?"
yea
that's exactly it, actually
When she becomes the wise woman (or rather when she becomes the hag), she helps prepare the loom of fate by stringing the warp to the frame. Or, that is to say, she finds those necessary to bring on that new era. In this lies her power as she transitions from the wise woman back to the warrior.
"When life springs from death."

The Transition Ceremony

When the Warrior is ready to take on the mantle and become the Morrigan in full, a ceremony takes place in the place where the wise woman was first chosen to take on the mantle herself. The ceremony is an acknowledgment of what is left behind when the mantle is taken. Not only must the chosen leave their families, but they must also watch their loved ones grow old and die. Some have seen the complete extinction of their villages and cultures as new generations move, or the village itself is destroyed during times of war. If such tragedies happen then, the chosen have been known to bury their loved ones and those they grew up with at their places of birth in a sacred burial ground. The Elder gods themselves then hide these. This is as much to help the chosen move on from their tragedy as it keeps these sites from being defiled by future settlers (whether by accident or on purpose). 
The ceremony takes place at dusk, the day before the spring equinox. The wise woman and Warrior stand across from each other—the wise woman holding ceremonial robes, jewelry, or garments of her culture. The Warrior wearing the armor of her own culture, decorated with the imagery of a crow. The staff of the Morrigan (ash with an iron casting of a crow) is handed from the wise woman to the Warrior. As it is passed to the Warrior, the staff changes to the weapon that the Warrior prefers and is carried in that form until the war's end. The Warrior then, in acknowledgment to the customs of death for the former Morrigans culture. Kills the wise woman concerning those customs that dictate where she will go in the afterlife. 
The wise woman is buried beside her long-dead relatives and friends, and at the dawn of the spring equinox, the Warrior is crowned as the Morrigan in full. 
When life springs from death

Type

Religious, Special