I would like to know what you guys has to say about this Giant of a man. I understand that he's a deity and that he served Shor till he died while protecting him from foreign gods.
I would like to know who these foreign gods were and why they attacked them. I would also like to know how he came to existence and why the hell does he look like a nord if he was suppose to be there before them or what??
Why is he massive? Was he born or created? Was he on Atmora or just on Tamriel?
Please share any knowledge you have of him, even if it's just rumors.

Ask the lore forum next time.

Tsun was the shield-thane of Shor. Shor is Lorkhan. Lorkhan was killed by Trinimac (who is now Malacath but that's a different story) who ripped out his heart. Auri-El then used his Bow to shoot Lorkhan's heart into the ground which creates Red Mountain.

Auri-El is the Altmeri equivalent of Akatosh and Trinimac is his knight.

Tsun probably fought alongside Shor/Lorkhan but died as well.

He looks like a Nord because that's the form a Nord would expect their hero God to look like.

EDIT: Also the early Nords fought alongside Shor against Auri-El. The Aldmer (progenitors to the Elven races) fought alongside Auri-El. That's why the Nords have a deep-rooted hatred of the Elves.

You can read up on Tsun at http://www.imperial-library.info/search/node/tsun
And this thread may be served better in the http://www.gamesas.com/forum/16-elder-scrolls-lore/ section of the forum.

Hope that helps