Background: Kagemaru was born into a prominent magic using family. His family were healers that were the well loved and respected by the Alfheim of the capital.
Kagemaru (his real name is unknown, possibly forgotten even to himself) displayed an innate gift for magic, and the healing arts.
He was abducted when he was a child and taken to Nipponeria, a far away walled land of mystery and pagodas. A thieves guild adopted him and named the strange boy with pointy ears, Kagemaru (Nipponerian for "Ghost of Shadows").
Under their tutalage, his naturally agile body quickly adapted to the rigors of becomming a thief.
His "rights of passage" was to steal four purses from anybody, then put the purses back on the persons. As soon as the task was easily accomplished, they threw Kagemaru a joyous celebration.
However, he never forgot his home and his family. Finally, he could not bear the pain any longer. With the guilds blessing, he left and went back home to where he once came.
When he returned, he found that his people had fled following a Shadow Elf invasion. He could not find his family and followed one group of refuges to Wendar, asking along the way where his family was. No one could answer his questions.
Finally he recieved his answer. He found his younger brother and twin sister dead in the back of a body disposal cart in Wendar. His mother and father were lying in a makeshift sicktent where healers and clerics were tending to those sick from the plague (which they had contracted from a group of infected Ethengarians as they were fleeing Alfheim). The clerics looked at his mother and father, shook their heads and tended to others that could be saved for they couldn't do anything because the end of the great war caused such destruction that all magic wasn't working ("The week without magic")
He went to his mother and noticed that she died in the arms of her husband, his father. He was about to turn around and walk out when his fathers hand grabbed him by the wrist.
"... Never Forget..."
With those dying words, something inside him stirred. He felt an unbelivable ammount of power surging through him. A great gust of wind swept out from his body, demolishing the tent and knocking many of the patients right out of their cots. The force of it nearly tore him in two, and he collapsed. When he came to, days later when magic was restored, he was told that the sages surmised that he had just found out how to open a gate through which raw magical energy could flow, despite the loss of all magic elsewhere on the planet that week. The Wendarian and Alfheim elves didn't know anything about this new type of magic. They tried bringing in experts from other lands to help him but no one knew what this power was. Finally they called in one more person, a novice Wendarian Bladesinger named Marcus. Marcus had been trained in the magical arts, in part, by a Flaem in Glantri and they figured that he might know of this power. He had heard something about it in passing but didn't know much about it. Marcus tried to help him control this power, but with little success, it was just too chaotic. Kagemaru eventually grew impatient waiting for Marcus to have a breakthrough as he was anxious to take revenge on the shadow elves that had killed his family and destroyed his country. He finally just left one day, saying only a few words.
"Revenge... I MUST HAVE REVENGE!!!!!"
Over time he has become better at harnessing and shaping that magic but it is still very volatile and dangerous. While he was learning to control it some people were hurt. He vowed that he would use his magic solely for revenge. He was a Wild Mage. His hatred and desire for revenge led him to proclaiming himseld an "assassin of shadow elves."
Player's notes: He has heard about a group of Alfheim elf refugees in Karameikos who have named them selves "the Alfheim Avengers" and who are planning to retake Alfheim by force. He is heading to Karameikos to find, and join the Alfheim Avengers.
DM's notes: Essentially he was a thief, advanced to a fairly good level, but now his anger has blinded his thought so much that he has turned to the assassin kit and has forfeit many of his previous thief abilities to be a multi class Wild Mage/ Thief. He has not actually killed a shadow elf yet and he may find that he really is not cut out for it, but now all he can see is his need for revenge.