Life is a fine cost its well worth it
In a fairly misinformed article on the value of Magic cards as a collectable entity, I saw this picture: Imagine that, but with all rarities and playability levels mixed together, six feet tall, and occupying a room
As usual, the higher the rarity of a Wildcard, the harder it is to obtain
This is playable in the role of a tutor if you are truly desperate
Typically, having very few cards in your library is a nightmare scenario, so cards like Doomsday or Leveler are trying to enact a harsh penalty that turns out to be a boon
It's amazing because it's a self-fueling engine: It mills cards and causes lands to leave your graveyard for its ability and others