This card is from Mythological Age, and expansion that introduces a new type of monsters, Spirits.  Much like Toons, Spirits all share similar advantages and disadvantages, and they are affected by cards that affect Spirits.  Unlike Toons, Spirits tend to be great monsters.

 

The basic use of this card is to completely lock-down your opponent.  If you can run your opponent out of options, you can use Eight Giant Crows to make sure that they don't draw any more.

 

First, pave the way for the little guy by destroying all traps and monsters(yes, indeed, easier said than done).  After that, if he can make it through, your opponent won't draw next turn.  At this point your opponent is stuck with what they have in their hand to try to take care of the Crow.  Only Traps and Quick-Play Magics will be able to take care of the Crow, because it goes back to your hand every turn.  Also, any sort of hand-destruction card can get rid of it, but if you play well, this is doubtful.

 

So, if you can take care of your opponent's last few options, they won't be able to draw for the rest of the game, leaving you free to do what you want.  This strategy can be slightly tricky to use, however, because to keep it going you won't be able to normal summon any other monsters.  To win, you will probably have to have monsters already in play, special summon other monsters, or my personal favorite, play an Exodia deck.  With an Exodia deck, at this point you just sit back and wait for the pieces of Exodia to come to you.

 

Basically, if you design your deck well and can get the Crow to work, you've won the game.  Because of this, Eight Giant Crows has been restricted to ONE per deck.  There had to be some sort of catch on a card this good, right? ^_^