Huh. Well, the name certainly fits: it's dependent on some other effect to make it any good at all. On its own it's worse than Darksteel Relic. However, that's not a good trait for a mythic to have. Mythics should stand alone, apart from extremely exceptional circumstances like Eye of Ugin. This looks like it should be a rare (if it should exist at all).

I changed it to rare. Your point was fair.

I also allowed it to be alive the turn it enters the battlefield. That allows for some voltron-y godness.

Much better.

This is in a really interesting place now. Awesome on turn 1, especially as it allows you to avoid blocking with other things that might die. But the moment anything dies (or gets countered or discarded or milled)... poof! They all disappear. Very interesting.

By the way, where's the art from? It's pretty cool, and I'm not sure if I recognise it from Magic or elsewhere, but there's no artist credit.

IT's from Avacyn Restored, I think. I can't think of the card name right now.
EDIT: Haunted Guardian.