Is there a way to defeat Vanguard (the first boss)?

Solution 1:

This FAQ seems to answer the question.

Here's the relevant part:

                BOSS BATTLE : VANGUARD [BV]

This boss wasn't meant to be defeated, but stories of the hardcore prevailing are many.

It has 2 slashes, a direct overhead slash, and a horizontal forward slash. Not only that, but it also has a body press attack when players attempt to flank it too much.

A tactic for winning, is to stay under it's sword arm, and keep slashing it, until it does it's body press attack. At that point, roll back, and then resume slashing it.

If you do win, you'll score yourself a [Gripless] katana, and a [Grey Demons Soul]

Either way, win or lose, you die. D:

Solution 2:

My roommate spent countless hours with that game last semester, so I do know that it is possible to defeat him and that you get something for it. I also know that with those bosses, it often helps to go and train up for boss fights.

Sorry I can't remember specifics, though.