The land gets destroyed by Blight before Balance can resolve.
However, Balance only counts the number of lands each player controls when it resolves. So it can't see the land Blight destroyed, and in any scenario you have to sacrifice ones less land than you would if the land hadn't be destroyed by Blight anyway.
Mother's controller can tap her to give protection from white to Mother herself. So it would only work if Mother of Runes is already tapped, or under summoning sickness.
608.2h. If an effect requires information from the game (such as the number of creatures on the battlefield), the answer is determined only once, when the effect is applied. If the effect requires information from a specific object, including the source of the ability itself, the effect uses the current information of that object if it's in the public zone it was expected to be in; if it's no longer in that zone, or if the effect has moved it from a public zone to a hidden zone, the effect uses the object's last known information. See rule 113.7a. If an ability states that an object does something, it's the object as it exists--or as it most recently existed--that does it, not the ability.
Notice the part about "last known information" is for "a specific object" (like "the sacrificed creature's power" in Fling). General information like "the number of artifacts and enchantments" or even "the greatest power among creatures" doesn't use LKI, and looks just at the present.
Dockside Extorsionist's ability checks the number of artifacts and enchantments on the battlefield at the moment the ability resolves. It doesn't look back to the moment it triggered.
Would agens ability trump maralens as far as exile versus hand?
Yes, just like it does with any other "tutor" effect.
The cards found in the search will be exiled rather than be put wherever the spell or ability tells the opponent to put them after finding them. Any other effects the spell or ability has will still apply. If such an effect refers to the found cards, it can see them in exile.
(2020-11-10)
Kefnet does not copy a spell. He copies a card from your hand. And then he allows you to cast that copy. Casting that copy counts for Magecraft, but creating the copy doesn't, because the card you drew and revealed was not a spell on the stack.
Opponent is relative to the controller of the creature.
Also, notice how Enforcer's ability is written. She doesn't constantly has Double Strike as long as her controller has more life; it is an ability that triggers only as the combat phase begins (and if the condition is true), with Enforcer gaining Double Strike from that moment until that turns ends. So once she has gained Double Strike she retains it even if her controller loses too much life to still be with more - or even if she changes control.
But as this happens during combat, and loyalty abilities are sorcery speed, you can't use Dihada to get control of Enforcer after she has gained Double Strike, and still attack with her that same combat.
If you had an instant speed steal effect, such as Act of Aggression, you could do it this way: at the beginning of combat on your turn, Enforcer's ability triggers. When this ability resolves, Enforcer gains Double Strike until end of turn. You now cast Act of Aggression, taking control of Enforcer. She still has Double Strike, so you can attack with her.
It's because of the "until Out of Time leaves the battlefield" phrasing for the phasing out effect.
610.4. Some one-shot effects cause a permanent to phase out "until" a specified event occurs. A second one-shot effect is created immediately after the specified event. This second one-shot effect causes the permanent to phase in.
610.4c. If a resolving triggered ability creates the initial one-shot effect that causes the permanent to phase out, and the specified event has already occurred before that one-shot effect would occur but after that ability triggered, the permanent doesn't phase out.
You are not casting the creature, just moving it from the graveyard to the battlefield (or to your hand). You can't choose an alternate casting cost such as Evoke if you're not casting the creature.
Also, a card's mana value (old "converted mana cost") is based on its mana cost on the top right corner. Meren sees Shriekmaw as a creature card with mana value/converted mana cost of 5, always.
3) Search for an equipment, and exile it. It never gets on the battlefield.
"It's in one sentence" is not relevant. If you want a rule of thumb, use this: one verb = one action. Even if they are on the same line or sentence or phrase, they are separated actions.
Giant's ability wants to do the following actions, in order: search; then put; then attach; then shuffle. Opposition Agent exiles the cards that is found during the "search" action, preventing the "put on the battlefield" action. The "attach" action also becomes impossible. Then, the player performs the "shuffle" action.
The cards found in the search will be exiled rather than be put wherever the spell or ability tells the opponent to put them after finding them. Any other effects the spell or ability has will still apply. If such an effect refers to the found cards, it can see them in exile.
(2020-11-10)
Wulfgar of Icewind Dale's last ability affects only triggered abilities with conditions that are directly related to attacking, such as "whenever this creature attacks" or "whenever you attack with one or more creatures." It does not affect triggered abilities with other trigger conditions, such as "whenever this creature becomes tapped."
So yes, it affects "whenever you attack" abilities. You attacking with a creature caused Overwhelming Instinct to trigger, so Wulfgar's static ability (his is not an "effect trigger") causes Instinct's ability to trigger twice.
You don't choose a land beforehand for Crack the Earth; you choose and sacrifice one land you have when Crack the Earth resolves. You don't have a window of time between choosing a land to sacrifice, and actually sacrificing it.
So you either sacrifice Ghost Quarter for Crack the Earth and not for its ability; or you use Quarter's ability in response, and end up having to sacrifice some other land to Crack the Earth.
The activated ability, when it resolves, would give to Mairsil the triggered ability "Whenever equipped creature deals combat damage to a player, that player loses the game". In order for this triggered ability to work, Mairsil would need to be an equipment equipped to a creature. Mairsil being a creature with an equipment wouldn't, ahem, cut it.
We don't yet have the full rules that explain how a d20 ability such as The Deck's works. My informed guess is that it's all a single activated ability, so it would work with Mairsil normally.
The M19 planeswalkers are Ajani, Tezzeret, Liliana, Sarkhan and Vivien. Of those, Tezzeret and Liliana are aligned with Bolas, while Sarkhan and Vivien have reasons to oppose him, so my guess is Ajani is recruiting them.
The land gets destroyed by Blight before Balance can resolve.
However, Balance only counts the number of lands each player controls when it resolves. So it can't see the land Blight destroyed, and in any scenario you have to sacrifice ones less land than you would if the land hadn't be destroyed by Blight anyway.
Mother's controller can tap her to give protection from white to Mother herself. So it would only work if Mother of Runes is already tapped, or under summoning sickness.
Notice the part about "last known information" is for "a specific object" (like "the sacrificed creature's power" in Fling). General information like "the number of artifacts and enchantments" or even "the greatest power among creatures" doesn't use LKI, and looks just at the present.
Yes, just like it does with any other "tutor" effect.
The cards found in the search will be exiled rather than be put wherever the spell or ability tells the opponent to put them after finding them. Any other effects the spell or ability has will still apply. If such an effect refers to the found cards, it can see them in exile.
(2020-11-10)
Also, notice how Enforcer's ability is written. She doesn't constantly has Double Strike as long as her controller has more life; it is an ability that triggers only as the combat phase begins (and if the condition is true), with Enforcer gaining Double Strike from that moment until that turns ends. So once she has gained Double Strike she retains it even if her controller loses too much life to still be with more - or even if she changes control.
But as this happens during combat, and loyalty abilities are sorcery speed, you can't use Dihada to get control of Enforcer after she has gained Double Strike, and still attack with her that same combat.
If you had an instant speed steal effect, such as Act of Aggression, you could do it this way: at the beginning of combat on your turn, Enforcer's ability triggers. When this ability resolves, Enforcer gains Double Strike until end of turn. You now cast Act of Aggression, taking control of Enforcer. She still has Double Strike, so you can attack with her.
So you have its End Step trigger, and then sacrifice it still in the same End Step, either in response to the trigger or after it has resolved.
610.4. Some one-shot effects cause a permanent to phase out "until" a specified event occurs. A second one-shot effect is created immediately after the specified event. This second one-shot effect causes the permanent to phase in.
610.4c. If a resolving triggered ability creates the initial one-shot effect that causes the permanent to phase out, and the specified event has already occurred before that one-shot effect would occur but after that ability triggered, the permanent doesn't phase out.
You are not casting the creature, just moving it from the graveyard to the battlefield (or to your hand). You can't choose an alternate casting cost such as Evoke if you're not casting the creature.
Also, a card's mana value (old "converted mana cost") is based on its mana cost on the top right corner. Meren sees Shriekmaw as a creature card with mana value/converted mana cost of 5, always.
"It's in one sentence" is not relevant. If you want a rule of thumb, use this: one verb = one action. Even if they are on the same line or sentence or phrase, they are separated actions.
Giant's ability wants to do the following actions, in order: search; then put; then attach; then shuffle. Opposition Agent exiles the cards that is found during the "search" action, preventing the "put on the battlefield" action. The "attach" action also becomes impossible. Then, the player performs the "shuffle" action.
The cards found in the search will be exiled rather than be put wherever the spell or ability tells the opponent to put them after finding them. Any other effects the spell or ability has will still apply. If such an effect refers to the found cards, it can see them in exile.
(2020-11-10)
So yes, it affects "whenever you attack" abilities. You attacking with a creature caused Overwhelming Instinct to trigger, so Wulfgar's static ability (his is not an "effect trigger") causes Instinct's ability to trigger twice.
You don't choose a land beforehand for Crack the Earth; you choose and sacrifice one land you have when Crack the Earth resolves. You don't have a window of time between choosing a land to sacrifice, and actually sacrificing it.
So you either sacrifice Ghost Quarter for Crack the Earth and not for its ability; or you use Quarter's ability in response, and end up having to sacrifice some other land to Crack the Earth.
We don't yet have the full rules that explain how a d20 ability such as The Deck's works. My informed guess is that it's all a single activated ability, so it would work with Mairsil normally.