Book of Moon
But it wouldn't be solar eclipse week without a
moon, as well as a sun.
What can I say about this card... Since it's
release in 2003, it was used in competitive decks
very often for an entire decade. Some players even
use it now. While many cards from 2003 have become
super broken or obsolete, Book of Moon has always
been categorically balanced.
I'll go on the record saying that Book of Moon is
the single most well-designed card in the game. Why?
1) It's very minimalist. It doesn't have a bunch
of irrelevant effects and needlessly long card text.
For a card with such a short effect, it manages to
have so many possible uses: block against battle,
re-use a flip effect (back when they were good),
protect a monster from face-up removal, prevent an
attack, block a combo, negate a floodgate monster.
2) It's never broken. It's almost to plus off of
this card because it's a -1 before anything is said
and done. It doesn't destroy anything or draw you
cards. However, the ability to undermine the
opponent's field or improve yours, depending on the
situation, can advance your overall game state.
3) It never had any negative baggage which could
make it obsolete. Usually, many cards which get
obsolete are too slow, a cost which is too high
(discard/payment/graveyard) or only work well with a
specific archetype. But nothing inherently prevents
a deck from using this card.
4) The terms of this card are broad. For example,
beatdown monsters means a lot to some formats (and
very little to others). Battle traps can be
defensive in some formats but slow in others. Also,
certain cards/trends are hot at certain moments. But
with Book of Moon, something as basic as
face-up/face-down position has kind of always been
important. Especially considering how monsters
always need to be face-up in order to activate their
effects and attack (and that's how you win in Yugioh).