Agreed with many of the other posters, this is good. We've been needing another way to defend permanents.
Also, I agree that this shouldn't be immortal. We've already shown that the Basilisk Blood combo isn't all that great, and what else are people gonna do? Blessing only gives one extra charge (and makes it vulnerable to Fire Buckler/Spine Carapace); Heavy Armor gives it two extra charges but that's hardly OP; Archangel gives it potentially infinite charges but only if you can keep both alive... I see the card being very useful, but not OP.