What is the prevailing view on his existence? Were his sons real too? Was he just a legendary creation for kings to claim lineage? If he truly existed what accomplishments can we attribute to him? Who/what resources do we rely on from the time period of his existence?
This is one of FAQ on the Vikings in this subreddit.
There will always to be said more, I'd especially recommend the first thread:
I'm also willing to answer some more follow-up questions, though not within 12 hours today.