Sadly, you may not want to go for this card if you are a serious player or duelist, thought it might be something to chase if you are a serious collector. First appearances would see this card as would be good because it requires a sacrifice, but that may not be true. In reality, you may end up sacrificing a much stronger card just to get the Dark Magician Knight into play.
The Knight starts off with an attack power of 2500 but requires that you sacrifice a card to summon the Knight. Since you must also have a Dark Magician in play, this usually means you have to sacrifice the that itself! In essence this means that you are trading the cards, and very little beyond that.
Myself, I can’t see much reason to put this card into your deck because it appears to be little more than a potential wasted card in your hand if you end up drawing it. Then why does a card like this exist? The best players actually question the use of a card with such little playable value.
Ultimately this card appears be just a collector’s item because it tends to be rather useless for real duel game play. Though if you want to create a deck full of magician cards as a collector, then you pretty much have to get a hold of this card. So if you are a player, then avoid this card for tournaments and fun duels. But watch for this card if you are trying to complete a magician set of cards.
Stronger and more useful cards can and do include the Dark Magician himself, the Chaos Magicians, and even potentially the Dark Magician Girl. Be careful and think things through when considering placing the Dark Magician Knight into your dueling deck.