Crystalline Nautilus — Journey into Nyx #34

Bestow (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached.)

When this permanent becomes the target of a spell or ability, sacrifice it.

Enchanted creature gets +4/+4 and has "When this creature becomes the target of a spell or ability, sacrifice it."