Altar of Dementia
Altar of Dementia
Sacrifice a creature: Target player puts a number of cards equal to the sacrificed creature’s power from the top of their library into their graveyard.
“It is not that you will go mad. It is that you will beg for madness.” —Volrath
illus. Brom # 218/254

Oracle Text
Sacrifice a creature: Target player puts a number of cards equal to the sacrificed creature’s power from the top of their library into their graveyard.
10 swing with a 1/1 would remove 50% hp while saccing it to this would lower his library by 20%
and a major chance to lose harder vs ressurect decks
why even?
mill just makes 0 sense
Opponent can have something that prevents you from attacking
Opponent can have something that prevents damage from attacking creatures
Opponent can have something that prevents all damage
Opponent can destroy attacking creatures before they can deal damage
Opponent can have something that prevents loss of game from 0 life
And there are far more things that do the above than which would stop that player from losing due to having no deck.
Also, it's useful for self-mill if you're playing Dredge and/or Delve strategy, or reanimator, or anything else that plays out of the graveyard.
Here's a simple example.
You have 20 goblin tokens. Your opponent has 20 Saproling tokens. You're in a complete stalemate. You both also have an Angelic Exaltation in play. So, you and your opponent have a choice each turn. Attack with 1 token which will get pumped to 21/21 or attacks with some random amount of your tokens. Neither one really does anything to advance the game. You're totally stalemated. Sure, if something had Trample the game would end pretty quick, but nothing has Trample.
You play Altar of Dementia. Attack with one goblin token. It becomes 21/21 until end of turn. Your opponent blocks with one saproling. The game is still stalemated. Sacrifice your token to the Altar of Dementia and they're losing 21 cards. That probably wins you the game.
There are plenty of situations where you've got temporarily huge creatures, but they don't accomplish anything without Trample. This is a stalemate breaker and also is an enabler for certain decks that want to mill themselves.