Forced to attack

Some effects say that a creature attacks this turn if able.

If, during a player’s declare attackers step, a creature is tapped, is affected by a spell or ability that says it can’t attack, or hasn’t been under that player’s control continuously since the turn began (and doesn’t have haste), then it doesn’t attack. If there’s a cost associated with having a creature attack, the player isn’t forced to pay that cost, so it doesn’t have to attack in that case either.

* The controller of each attacking creature still chooses which player or planeswalker that creature attacks, unless something says otherwise.

* If a creature that can’t attack alone also must attack if able, its controller must attack with it and another creature if able.

* If there is an additional combat phase in a turn, and such a creature has already attacked, it is not required to attack again.

Some effects say that a creature attacks each combat if able. All of the above is also true regarding them, with one exception –  If there is an additional combat phase in a turn, and such a creature has already attacked, it is required to attack again if able.

* If Insatiable Gorgers hasn’t been under your control since the turn began, is tapped, or is affected by a spell or ability that says it can’t attack, then it doesn’t attack. If there’s a cost associated with having it attack, you aren’t forced to pay that cost, so it doesn’t have to attack in that case either.

Enters the battlefield attacking

If an effect puts a creature onto the battlefield tapped and attacking, the controller of that effect chooses which opponent or planeswalker controlled by an opponent the creature is attacking. Notably, the creature is never declared as an attacking creature, so this won’t cause any abilities that trigger “whenever a creature attacks” to trigger.

* You declare which player or planeswalker the token is attacking as you put it onto the battlefield. It doesn’t have to be the same player or planeswalker Inexorable Blob is attacking.

* Although the token is attacking, it was never declared as an attacking creature (for purposes of abilities that trigger whenever a creature attacks, for example).

Can’t be blocked

If a spell or ability lets your creature become one that can’t be blocked, you need to do it before blockers are declared.

* Activating Deepfathom Skulker’s last ability after it’s been legally blocked won’t change or undo that block. The declare attackers step is the last time you can activate the ability and have it be effective.

Forced to block

* If multiple attacking creatures must be blocked if able, the defending player must assign at least one blocker to each of them if possible. For example, if two such creatures were attacking and there were two potential blockers, they couldn’t both be assigned to block the same attacker.

* If a creature with Menace must be blocked if able, the defending player must assign at least two blockers if possible.

* If an effect says that “all creatures able to block a specific creature do so”, that effect doesn’t give other creatures the ability to block that specific creature. Rather, it simply forces those creatures which are already able to block that creature to do so.

* If a creature can’t legally block such an attacker, it can block another attacking creature. For example, the attacking creature that needs to be blocked has flying, and the other creature doesn’t have flying nor reach.

* If an attacking creature has “all creatures able to block this do so”, and during its controller’s declare blockers step, a creature the defending player controls is tapped or is affected by a spell or ability that says it can’t block, then it doesn’t block. If there’s a cost associated with having it block, its controller isn’t forced to pay that cost. If he or she doesn’t, the creature doesn’t have to block.

* If multiple attacking creatures have “all creatures able to block this do so”, the controller of each creature that could block them chooses which one that creature blocks. In this case, creatures that can block multiple creatures must block as many attacking creatures with that ability as possible.

Time to move on to noncombat damage
Would you like those burned?

Some spells deal N damage divided as you choose among any number of target creatures and/or players.

You divide the damage as you cast the spell, not as it resolves. The number of targets chosen must be at least 1 and at most N, where each target must be assigned at least 1 damage. That division can’t be changed later on.

If one of the targets is a player, you may deal that damage as it resolves to a planeswalker that player controls instead. “Instead” means you can’t deal damage to both a player and a planeswalker that player controls, you can’t deal damage to more than one planeswalker, and you can’t split the damage between the player and the planeswalker.

* You announce how the damage will be divided as part of casting Avacyn’s Judgment. Each chosen target must receive at least 1 damage.

* You can redirect damage that Avacyn’s Judgment would deal to an opponent to a planeswalker that player controls. However, Avacyn’s Judgment can’t deal damage to both a planeswalker and that planeswalker’s controller.

* If Avacyn’s Judgment has multiple targets, and some but not all of them are illegal targets when Avacyn’s Judgment resolves, Avacyn’s Judgment will still deal damage to the remaining legal targets according to the original damage division.

* If an effect creates a copy of such a spell, the division of damage and number of targets can’t be changed. The effect that creates the copy may allow you to change targets, however.

Your order matters to us

As mentioned above, if noncombat damage would be dealt to an opponent by a source you control, You may have that source deal that damage to a planeswalker that opponent controls instead. This is known as the “planeswalker redirection effect”, which is one kind of replacement effects.

If multiple prevention and/or replacement effects are trying to apply to the same damage, the player who would be dealt damage (and who controls the planeswalker that would be affected) chooses the order in which to apply them. The order might matter, and even cause the followings effects in that order to no longer be applicable.

* If multiple replacement effects could apply to damage being dealt to you or Goldnight Castigator, you choose the order to apply those effects. Notably, if a source an opponent controls would deal noncombat damage to you while you control a planeswalker, you can have that opponent choose whether or not to redirect the damage to that planeswalker before the damage is doubled. If you do, damage redirected to that planeswalker won’t be doubled.

Another example

* If multiple prevention and/or replacement effects are trying to apply to the same damage, the player who would be dealt damage chooses the order in which to apply them. Notably, if noncombat damage would be dealt to you by a source controlled by an opponent, you choose the order in which to apply Deflecting Palm and the planeswalker redirection effect. If you apply Deflecting Palm first, the damage will be prevented (and damage will be dealt to the source’s controller) and the planeswalker redirection effect won’t apply.

To conclude this post, here are a few words about fights

It takes two to tango

Some abilities, like “Fight” (and the less common “Exchange”) require 2 legal targets in order to resolve. For such abilities, if the entire ability can’t be completed, no part of it occurs. If even one of the targets is illegal on resolution, nothing will happen.

* If the creature you control becomes an illegal target (perhaps due to being destroyed by another spell or ability), Unnatural Aggression will resolve, but the target creature an opponent controls will neither deal nor receive any damage. If that creature would die later in the turn for another reason, it will be exiled instead.

* If either of the creatures that were chosen to fight become illegal targets as the spell tries to resolve, neither creature will deal or be dealt damage during the resolution of the spell.

* If the creature an opponent controls survives the fight but would die later in the turn for another reason, it will be exiled instead, whether your creature dealt it damage or not.