Sift N(Reveal N random cards in your graveyard and exile one of them.)
For example:
3B
Sorcery (C)
Sift 3, then draw X cards and lose X life, where X is the converted mana cost of the exiled card.
The idea is to give the player a way to use their graveyard as a resource. There are numerous mechanics that already do this in one way or another, but they are all either very difficult to balance or very restricted. I came up with Sift in an attempt to find a middle ground.
The most noticeable quirk about Sift is that it doesn't actually do anything on its own. In that respect, it plays a lot like Imprint, a highly successful mechanic. I wanted to play around in the same space, allowing you to "sift" through your graveyard to find the card that would be best used in the current situation. Selecting a card and exiling it, then having an effect that cares in some way about the exiled card felt pretty good, but had some problems:
1. It was a tad too powerful. With the amount of fuel this set needs for its graveyards, the selection is pretty big, giving the player too much power over what the spell ends up doing.
2. If there are too many choices, gameplay slows down a lot. Mechanics like Dredge have proven to slow down play due to giving the player too many choices of what cards to use for an effect.
To mitigate these problems, I limited the choice to one out of a randomly selected group of cards in your graveyard (usually two cards). Players will decide more quickly between two or three cards than they will between five or six. Also, obviously, the smaller selection gives less power to the player. This ultimately makes the decision much more compelling. Here are some other examples:
XG
Instant (R)
Sift X.
You may cast the exiled card for as long as it remains exiled.
A Regrowth effect that scales in reverse with how many cards are in your graveyard.
4G
Creature - Elf Shaman (U)
At the beginning of your upkeep, sift 2. Create a 1/1 green Saproling creature token if the exiled card was a creature card. You gain 2 life if it was a land card. Draw a card if it was a noncreature, nonland card.
2/4
4B
Enchantment (U)
At the beginning of your upkeep, sift 2. Each opponent loses X life and you gain X life where X is the exiled card's converted mana cost.
At the beginning of your end step, put the top two cards of your library into your graveyard.
Uncommon repeated payoffs for limited.
BB
Creature - Spirit (R)
You may cast ~ from exile.
Haste
At the beginning of your upkeep, if ~ is in your graveyard, sift 2.
2/1
A mechanical twist that encourages you to try and sift this guy away by its own effect.
You mentioned slowing down the game by giving too many options, but the random element will end up slowing games far more than a flat choice. As is, it seems there is rarely a plethora of choices for your cards. The ability reads as a more complicated Imprint. The problem of too much control over the effect is actually something you probably want. If the effects are too strong when they have complete control then you should probably scale back the effects not remove the control.
The randomness really hurts here. Doing any kind of random selection with the graveyard in formats with older cards (Legacy, Vintage, EDH) is a huge pain because you're not allowed to shuffle or rearrange your graveyard. On top of that, your first, second, and fourth examples have a chance to whiff entirely if they hit a land, making this mechanic an example of unacceptable randomness instead of one with just unequally beneficial outcomes.
The most similar card I would compare to this is Tasigur, the Golden Fang, who at least counterbalanced the lack of control over his activated ability with a very powerful graveyard sculpting tool upfront.
For example:
3B
Sorcery (C)
Sift 3, then draw X cards and lose X life, where X is the converted mana cost of the exiled card.
The idea is to give the player a way to use their graveyard as a resource. There are numerous mechanics that already do this in one way or another, but they are all either very difficult to balance or very restricted. I came up with Sift in an attempt to find a middle ground.
The most noticeable quirk about Sift is that it doesn't actually do anything on its own. In that respect, it plays a lot like Imprint, a highly successful mechanic. I wanted to play around in the same space, allowing you to "sift" through your graveyard to find the card that would be best used in the current situation. Selecting a card and exiling it, then having an effect that cares in some way about the exiled card felt pretty good, but had some problems:
1. It was a tad too powerful. With the amount of fuel this set needs for its graveyards, the selection is pretty big, giving the player too much power over what the spell ends up doing.
2. If there are too many choices, gameplay slows down a lot. Mechanics like Dredge have proven to slow down play due to giving the player too many choices of what cards to use for an effect.
To mitigate these problems, I limited the choice to one out of a randomly selected group of cards in your graveyard (usually two cards). Players will decide more quickly between two or three cards than they will between five or six. Also, obviously, the smaller selection gives less power to the player. This ultimately makes the decision much more compelling. Here are some other examples:
XG
Instant (R)
Sift X.
You may cast the exiled card for as long as it remains exiled.
A Regrowth effect that scales in reverse with how many cards are in your graveyard.
4G
Creature - Elf Shaman (U)
At the beginning of your upkeep, sift 2. Create a 1/1 green Saproling creature token if the exiled card was a creature card. You gain 2 life if it was a land card. Draw a card if it was a noncreature, nonland card.
2/4
4B
Enchantment (U)
At the beginning of your upkeep, sift 2. Each opponent loses X life and you gain X life where X is the exiled card's converted mana cost.
At the beginning of your end step, put the top two cards of your library into your graveyard.
Uncommon repeated payoffs for limited.
BB
Creature - Spirit (R)
You may cast ~ from exile.
Haste
At the beginning of your upkeep, if ~ is in your graveyard, sift 2.
2/1
A mechanical twist that encourages you to try and sift this guy away by its own effect.
Anyway, what do you guys think?
The most similar card I would compare to this is Tasigur, the Golden Fang, who at least counterbalanced the lack of control over his activated ability with a very powerful graveyard sculpting tool upfront.