GENERAL QUESTIONS
Alternative Play Costs (APCs)

Q: Some cards have a condition that must be true to play them with their alternative play costs (APCs). For example, Lashknife's APC reads, "If you control a plains, you may tap an untapped creature you control instead of paying Lashknife's mana cost." When do you check to see if that condition is true?

A: The condition must only be true when you announce you're playing the spell. If the condition isn't true later, you don't have to back up and pay the mana cost.

Q: What happens if something that makes me pay additional mana to play a spell (Gloom and Squeeze, for example) is in effect when I try to play a spell by paying its APC?

A: Paying for a spell with its APC only gets you out of paying the spell's mana cost. All other costs must still be paid, including those imposed by effects such as Gloom's.
Fading

Q: How exactly does this ability work?

A: Fading is an ability that causes permanents to stay in play for a limited time. Cards with fading come into play with a specified number of fade counters on them. They also have a triggered ability that forces you to remove one of these counters at the beginning of each of your upkeeps. When you try to remove a fade counter and there are none left to remove, you must sacrifice the permanent.

Q: Why do some of the cards with fading have no reminder text?

A: On a few cards, the reminder text for fading simply wouldn't fit in the text box. Fading works the same on every card, though, whether it has reminder text or not.

Q: Do I have to sacrifice the permanent with fading as soon as I remove the last fade counter from it?

A: No. The permanent sticks around until you try to remove a fade counter when there aren't any left to remove. Fading works similarly to being "decked"--you don't lose when you draw your last card, you lose when you have to draw a card and can't.

Q: What if I forget to remove a fade counter?

A: The triggered ability that makes you remove fade counters is mandatory, not optional, so you must back up and remove a counter. (If there are none left to remove, you must back up and sacrifice the permanent.)
Laccolith Creatures

Q: How does the ability on the laccolith creatures work?

A: The laccoliths have an ability that enables them to deal damage directly to a target creature instead of dealing combat damage to creatures blocking them. It triggers whenever the laccolith becomes blocked. When it triggers, you choose a target creature. When it resolves, you decide whether to use the ability or deal the laccolith's combat damage normally.

Q: What happens if a creature with first strike blocks a laccolith creature?

A: If the laccolith's controller decides to use its ability, the laccolith deals damage first. This is because the laccolith ability triggers and resolves during the declare blockers step--long before the time during the combat damage step when creatures with first strike deal their combat damage.

Q: Can I use a laccolith's ability to deal damage directly to a creature blocking it?

A: Yes, but if you do, the laccolith won't deal its combat damage that turn.

Q: Does a laccolith's ability trigger if I block it with an effect like Trap Runner's or Fog Patch's?

A: Yes, because the ability doesn't say "blocked by a creature."
Mercenaries/Rebels

Q: If an effect tells me to search my library for a Mercenary or Rebel card and put it into play, do I have to?

A: No. You can choose not to find a card of the specified type. (If this rule didn't exist, judges at tournaments would have to verify that you didn't have cards of the type you're supposed to search for.)
CARD-SPECIFIC QUESTIONS
Accumulated Knowledge

Q: When I count the number of Accumulated Knowledge cards in graveyards, do I get to count the one that's resolving?

A: No. Accumulated Knowledge is still on the stack while it's resolving, not in a graveyard.
Angelic Favor

Q: If I play this during my end step, can I keep the Angel token and attack with it during my next turn?

A: No. Angelic Favor reads, "Play Angelic Favor only during combat," so you can't pull off the old Waylay trick.
Animate Land

Q: Can I play Animate Land on one of my lands and then attack with it?

A: Yes--if the land has begun the turn under your control. Otherwise, you'd have to give it haste if you wanted to attack with it.
Chieftain en-Dal

Q: When it attacks, will it give itself first strike?

A: Yes. (If it didn't, it would read, "all other attacking creatures gain first strike.")
Coiling Woodworm

Q: Does its ability count my opponent's forests?

A: Yes. (If it didn't, it would read, "the number of forests you control.")
Defiant Falcon

Q: Does this count as a Rebel card for effects that search for Rebels?

A: Yes. Each separate word that appears after "Creature -- " on a creature card gives it a creature type. Defiant Falcon is a "Rebel Bird," so it has two creature types: Rebel and Bird.
Divining Witch

Q: When I play its ability, when do I have to name a card?

A: You name the card as the first step of resolving the ability.
Flowstone Overseer

Q: Can I target my opponent's creature with the Flowstone Overseer's ability?

A: Yep. (If you couldn't, it would read, "target creature you control.")
Fog Patch

Q: Let's say my opponent attacks me with a creature with trample. I don't block it, but I play Fog Patch. What happens?

A: Fog Patch's effect will block the creature, but that effect doesn't have a toughness value like a blocking creature would. This means all the attacking creature's damage will "trample through."
Kill Switch

Q: Can I choose to leave Kill Switch tapped during my untap step?

A: No.
Mana Cache

Q: Is the second ability a mana ability?

A: Yes, regardless of who's playing the ability.
Netter en-Dal

Q: If I play its ability on a creature that's already attacking, does that creature leave combat?

A: No. Once a creature is declared as an attacker, it's too late--the Netter's ability can't stop it.
Noble Stand

Q: How much life do I gain if one of my creatures blocks multiple attackers (such as Wall of Glare)?

A: You gain only 2 life. Noble Stand's ability triggers only once for each creature that blocks, not once for each attacking creature that gets blocked.
Off Balance

See Netter en-Dal.
Oracle's Attendants

Q: What happens if, after the ability resolves, Oracle's Attendants isn't in play when the target creature is dealt some damage?

A: As worded, the damage will end up being dealt to nothing. That's why we had to update the wording on Oracle's Attendants. It should read, "T: All damage that would be dealt to target creature this turn by a source of your choice is dealt to Oracle's Attendants instead as long as both are creatures in play."
Overlaid Terrain

Q: Can I tap my lands for double mana before Overlaid Terrain makes me sacrifice them?

A: No. Overlaid Terrain reads, "As Overlaid Terrain comes into play, sacrifice all lands you control." This means that you sacrifice them at the same time you're putting Overlaid Terrain into play. By the time Overlaid Terrain's continuous effect is "on," your lands are already in your graveyard.
Pale Moon

Q: If I tap a land that produces more than one mana (such as Lotus Vale), how much colorless mana do I get?

A: Pale Moon doesn't change the amount of mana being produced, only the type. With Pale Moon in effect, Lotus Vale would produce three colorless mana.
Parallax Wave/Nexus/Tide

Q: When Parallax Wave leaves play, will it return all cards removed from the game with any Parallax Wave?

A: No. When a card refers to itself, it refers to only that copy of the card, not others with the same name. This means each Parallax Wave keeps track of the cards it removed from the game separately. When the Wave leaves play, it will return only the cards it removed, not cards removed by other Parallax Waves. The same is true for Parallax Nexus and Parallax Tide.

Q: What happens if I activate Parallax Wave's ability multiple times and then destroy it before the activated abilities have a chance to resolve?

A: The Wave's leaves-play ability would trigger and go on the stack, on top of the activations that haven't yet resolved. That triggered ability would then resolve, returning to play all cards removed with the Wave--but none have been removed yet. Then the activations resolve, removing creatures from the game. The removals are permanent, because the Wave is already gone. The same is true for Parallax Nexus and Parallax Tide. This timing trick mandates a slight rewording of these three cards. Here it is:

Fading 5
Remove a fade counter from Parallax Wave: Remove
target creature from the game if Parallax Wave is
in play.
When Parallax Wave leaves play, each player
returns to play all cards other than Parallax
Wave he or she owns removed from the game with
Parallax Wave.

This wording means if the Wave is no longer in play when its activated ability tries to resolve, the target creature won't be removed from the game. Parallax Nexus and Parallax Tide get similar corrections, but without the "other than this card" restriction:

Fading 5
Remove a fade counter from Parallax Tide: Remove
target land from the game if Parallax Tide is in
play.
When Parallax Tide leaves play, each player returns
to play all cards he or she owns removed from the
game with Parallax Tide.

Fading 5
Remove a fade counter from Parallax Nexus: Target
opponent removes a card in his or her hand from the
game if Parallax Nexus is in play. Play this ability
only if you could play a sorcery.
When Parallax Nexus leaves play, each player returns
to his or her hand all cards he or she owns removed
from the game with Parallax Nexus.

Q: How does Parallax Wave interact with Opalescence?

A: The corrected wording stops weird tricks involving Parallax Wave removing itself from the game while Opalescence is in play.
Spiteful Bully

Q: Can I have the Bully deal damage to itself?

A: Sure. The Bully's ability doesn't say, "another target creature," so it can target itself. (In fact, if the Bully is the only creature in play, it must target itself.)
Stronghold Gambit

Q: What happens to cards that aren't put into play?

A: They remain in their owners' hands, and they don't stay revealed.

Q: What happens if neither player chooses a creature card?

A: Nothing is put into play. When Stronghold Gambit resolves, everyone reveals a card, but only the creature cards and their mana costs matter. Noncreature cards simply stay in their owners' hands.
Terrain Generator

Q: If I play Terrain Generator's second ability during my turn, does it count as my one land play for the turn?

A: No. Using a spell or ability to put a land into play doesn't count as your once-a-turn land play.
Topple

Q: When does this spell check to see which creature has the greatest power?

A: Topple reads, "target creature with the greatest power." This means you can target only the creature with the greatest power when you play Topple. When it resolves, if your chosen target no longer has the greatest power (or is at least tied for greatest), it's no longer a valid target and Topple will be countered.