This card may have been effective in its original form, which allowed you to activate to take  

2 cards per 2 generic mana; but with the addition of a tap, the card is basically useless.

Newer sets allow for the mass-destruction of the opponent's library, rendering something

like this irrelevant. That said, I don't like library destruction. Winning by running the other

player out of cards is just a petty trick, and I'd like to see the game mature beyond the

popularity of such a cheap, dissatisfying victory. In fact, it might bring millstone back into

relevance as a tactic, combo-ing a return to the top of the library, and straight down to the

grave. The problem you would find with using that combo today, of course, is the popularity

of graveyard returning spells - And by doing it, you would only be displacing the card for a  

turn, perhaps. It might be more reasonable to limit the strength of cards that return things

from the grave, in the future.I understand that making a game like this would certainly

stretch the mind, in looking for new ideas for a spell, but a lot of what is being included as

legal in the major formats is really, very over-powered. I would eliminate every card that can

make a "dazzling", one-play turn around of the whole game for the win. When it seems to

you that you lost for no good reason, rather than scolding yourself for not foreseeing the

surprise, consider that the play made was only some kid using a game-genie.
Eighth Edition
8ED Artifact