Nice card!

Vanguard is really interesting. Do you know how it plays?

My biggest worry is it may often not make much difference, but I'm excited because it's simple and intuitive to understand, and it makes combat more interesting without being much more complicated, which is the best thing possible for a new keyword.

It's bound to be relevant. You must have played with or against Taunting Elf, yes? This isn't that, but it's kind of crazy how many games that elf could completely swing by just forcing dumb blocks into it.

It's less strict than Lure though; this only comes into play if you have insufficient blockers. (Mind you, deathtouch on this one is a pretty nice compensation - target opponent must sacrifice a creature; maybe more than one.)

I do like it. I'd be worried that all too often you may end up with "Yeah; but they all have vanguard, so whatever" and "Ok, I have to block it. I was gonna do that anyway" (and it's not MUCH different from '~ must be blocked'; though it is slightly)

So yeah, it's a small ability, it's very flavourful and properly used it's likely to be very effective. I like it.