Wow. Nice tweak on Caltrops or Powerstone Minefield, but isn't it a bit strong? With just a couple of tokens or walls it's a one-sided Powerstone Minefield; with 4 it's a completely impenetrable defence from all but the largest creatures, and evasion is no help at all.

Yeah, good point. It would be fine at a higher CMC, though, don't you think?

"Creatures which attack you are destroyed" probably isn't an interesting enchantment at any cost. It's not fun to play (I mean... you cast it, it's a no brainer; why wouldn't you?) it's not fun to play against.

Maybe if the damage happens after the creatures hit you? The at least it's slightly interactive.

I would find this fun to play. :-( If you control enough creatures, though, it does work out similarly to Blazing Archon, which means it should have a higher converted mana cost. However, like Blazing Archon, this is susceptible to creature removal. If your board gets wiped, this is useless.
Maybe this would be more interesting as a creature with "Whenever ~ blocks a creature, each creature you control deals 1 damage to that creature."