If you do, draw X cards, then you may put a permanent card with mana value X or less from your hand onto the battlefield, where X is the sacrificed creature's mana value
It was auctioned off by PWCC towards the end of 2020 and sold for more than $35,000
Still, if you ever make this and instantly (or post blocking in enemy turn) tap 3 dorks to draw, with the threat of doing that again the following turn, you will love this card
In this case, however, the term "proxy" may no longer be applicable, as these cannot be considered substitutes for existing objects
Take, as a very good counter-example, Yuriko, the Tiger's Shadow
The most obvious oddity is the fact that it has the Magic: The Gathering card back, but there are also a few other differences, like a gold border instead of the classic yellow