However, doesn't this card kind of nullify itself? If you draw this card, you now must sacrifice a creature to get to the card you would have otherwise gotten, had you left this card out of the deck... Sundial and hourglass counter this by serving dual purposes (sundial) and lasting more than one turn at no significant cost (hourglass).
This card has multiple purposes:
1- Exchanging one of your creatures with a new card. This is the one that you observed to be nullifying. Unlike Hourglass, it is not "almost free" to draw a new card. You would hardly sacrifice your dragon for a new card, but you can trade a rendered useless creature such as a frozen creature, a creature with low AP in case your opponent has a shield that nullifies its damage, a creature that is most likely going to be eaten by an Otyugh.
2- Disposing a harmful creature: This permanent counters Antimatter and malignant cell till the end of game unless its destroyed.
3- Combo with creature generating. You can eat up your own zombies which aren't really a card you played, or you can sacrifice fractaled creatures.
4- Gives you a way to control your Bone Wall's charges. Hence; shreding bones of a creature you own to defend yourself.
5- Provides another way to draw a card since it asks no quanta.
The card can be tweaked while keeping the general idea of sacrificing a creature for a card. Please do tell me what you think. Thank you.
Some examples with increased effects and casting cost;
Healing Necro;
Bone Wall generating Necro; Doesn't replace your current shield unless its already Bone Wall, in which case it adds charges. (2 from Bone Wall + 2 from this card)