So this card is pretty open-ended, mechanically speaking, but that's half the fun. It doesn't explicitly reduce the AC of metal armor/shields, but it's also written such that it'll affect all non-magical metal objects. It won't instantly crack open a bank vault or disarm an attacker, but it will make a mess out of things, given enough time.

The real fun, of course, comes from giving the sixteen teeth to NPCs and seeing what happens.