If you go over to Gatherer, you'll see that
Panharmonicon already has a whole bunch of
rulings about its operation. I think that's a
little funny, because it's such a simple card at
heart. There are surprisingly few creatures with
comes-into-play abilities that can't be used
somewhere - it's a little overkill for
competitive Magic, but in casual and multiplayer
settings, a Panharmonicon can put you far ahead
of other people's defenses and ahead of EDH's
characteristic big plays. I never thought there
would be any way to make Terastodon more scary,
but that's not even the most impressive thing
about this card: Panharmonicon isn't legendary.
This is...interesting. It's a giga-Strionic
Resonator, causing abilities to trigger multiple
times. Think along the lines of extra life gain
off of Soul Warden and its brethren, extra
Purphoros damage triggers, and all that. The
possibilities are endless with this card, which
makes it promising.
The downside, of course, is that it's attached
to a four mana artifact with no impact on the
board state, outside of maybe what it triggers
entering play. I can see this being part of a
degenerate combo somewhere, but I think this
really needs a carefully-tuned shell to work.
