Thanks for posting! Nice character, however there are only a few problems which I would like to address.

[quote=kingkonrad]
The Serpent
[/quote]

What has he done to gain that nickname?

[quote=kingkonrad]
crossbow
[/quote]

Remember that this is supposed to be a faux ninth century. A crossbow is way too advanced as a device for this age, especially in the hands of a Norseman. 

[quote=kingkonrad]
Lindisfarne
[/quote]

Considering that your character is 31 (thus born in 845, considering that the current year is 876), this isn't quite possible, because the raid on Lindisfarne more than fifty years earlier in the timeline. Also, a Viking realm (Beornice) was estabilished in that region of England before your character was even born. 

[quote=kingkonrad]
re-establish the weakened hold over the Isle of Man
[/quote] 

In the current timeline, Manx is actually already a well-estabilished Norse realm. Your character's task might be that of convincing the various Viking lords of the isles to bend the knee to the king of Norway rather than conquer new lands in his name.

In general, since I'm going to post very soon a description of the various Viking realms of the isles, I suggest you to read that and then correct or rewrite your backstory.