It is now time to take a look on the most interesting phase of the turn – combat phase. Besides a fact, that there are a lot of triggers happening in that phase it’s a source for triggered events.
Combat phase starts with the beginning of combat step. This moment is a dot on a timeline where all triggers “At the beginning of combat…” triggers. This is happening before active player receives priority at the beginning of combat.
Basically, there is nothing complicated besides using official tournament shortcuts. Saying “Go to attack” will lead a game into different phases depending on the permanents with that kind of triggers. All details are in the shortcut article.
On declare attackers’ step everything is easy:
508.2a Abilities that trigger on a creature attacking trigger only at the point the creature is declared as an attacker…
In this rule the most important words are “declared as an attacker”. Not all attacking creatures has been declared attacking. For example, an Angel token from Geist of Saint Traft’s ability enters the battlefield already attacking. Active player has not declared it as an attacker. Its status has been defined by an effect, which created it. This means, that attacking with that creature does not cause “whenever a creature attacks” trigger to trigger.
Opponent’s Kazuul, Tyrant of the Cliffs trigger will work when Hero of Bladehold is declared as an attacker, but not when Soldier tokens are created tapped and attacking.
(508.2a) They would not work if a creature was declared as an attacker first and then its characteristics change and meet requirements for a triggered ability.
Example: a permanent has an ability “whenever green creature attacks, destroy it at the end of the combat”. If a blue creature has been declared as an attacker and then it became green, that ability will not be triggered.
You cannot declare attackers and then increase Aurelia’s power for its Mentor to work.
If you have declared 2 attacking creatures and then one of them left the battlefield, Exalted trigger will not work.
Triggers, that trigger on declare attackers’ step are going to the stack and resolve before combat step begins.
It’s getting way more fun on the declare blockers step:
509.5a Ability that says “whenever [a creature] blocks…” usually triggers only once during combat for that creature, even if it is blocking several creatures. This ability triggers when a creature is declared as blocker. It will also trigger if it became blocking as a result of effect, but only if it was not already declared as blocking (see rule 509.1g). Ability will not be triggered if a creature has been put on the battlefield blocking.
509.5b Ability that says “whenever [a creature] blocks a creature…” triggers once for each creature blocked with that ability. It will also trigger if it became blocking as a result of effect, but only if it was not already declared as blocking for that attacking creature. Ability will not be triggered if a creature has been put on the battlefield blocking.
However, in the triggering moment nothing special is not happening in a game. Despite a fact, that “triggers don’t have laws”, when they are triggered, they are waiting for their turn to be put on the stack. It will happen only next time when a player receives a priority.
The only exception from a rule is triggered mana abilities. They do not use the stack and resolves after being triggered.
509.5c Ability that says “whenever [a creature] becomes blocked…” usually triggers only once during combat for that creature, even if it is blocked be several creatures. It will be triggered if that creature will become blocked by a creature, which has already been declared blocking. It will also trigger if it became blocking as a result of effect or a creature that has been put on the battlefield blocking, but only if a creature with ability was not blocked before (see rule 509.1h).
509.5d Ability that says “whenever [a creature] becomes blocked by a creature…” triggers for each creature that is blocking. It triggers if a blocking creature has been declared as a blocker. It will also trigger if it became blocking as a result of effect, but only if it was not already declared as blocking for that attacking creature. Besides that, this ability will trigger if another creature has been put on the battlefield blocking that attacking creature. It will not trigger if a creature became blocked as a result of some kind of effect, not by creature.
509.5e If the ability triggers whenever a creature is blocking or becoming blocked by a specific number of creatures, that ability will trigger when this creature is blocking or being blocked during declare blockers step. Effects, that add or remove blockers and be a cause of triggering these abilities as well. This is fair for abilities, which triggers when a creature is blocking or becoming blocked by a minimum number of creatures.
509.5f If an ability triggers whenever a creature with a certain characteristic is blocking, it will only work if that creature had that characteristic at the moment when its declared as a blocker or became blocking due to some effect. If an ability triggers whenever a creature with a certain characteristic is blocked, it will trigger only if a creature had that characteristic when it became blocked. If an ability triggers whenever a creature is blocked by a creature with certain characteristic, it will be triggered if a blocking creature had that characteristic when it became blocking. None of the abilities above will not be triggered if a creature gets characteristic, suitable for an ability later.
Example: a creature has “whenever this creature is blocked by a white creature, destroy that creature at the end of combat” ability. If that creature is blocked by a black creature, which became white after it blocked, the ability will not be triggered.
Arrogant Bloodlord’s trigger is checking both blocking and attacking creatures for their size. If you have blocked Bloodlord with a Bear and then made it smaller, Bloodlord’s ability will not be triggered.
If a Bear equipped with Wooden Stake is blocking or becoming blocked with a 5/5 not a Vampire creature and then it’s becoming a Vampire, Wooden Stake’s ability will not be triggered. A creature will not be destroyed.
509.5g An ability that reads “Whenever [a creature] attacks and isn’t blocked,…” triggers if no creatures are declared as blockers for that creature. It will trigger even if the creature was never declared as an attacker (for example, if it entered the battlefield attacking). It won’t trigger if the attacking creature is blocked and then all its blockers are removed from combat.
Combat damage is damage, that is dealt by attacking or blocking creatures as a result of combat.
Benalish Cavalry is blocked by two 2/2 bear creatures. What is the most predictable combat outcome?
Happy end, everyone is dead. Because two creatures have been declared as blockers, flanking will be triggered twice. Both bears will become 1/1 on trigger’s resolution. Therefore, their powers will be equal in this deadly combat.
Because Markov Blademaster is not dealing any damage on the first damage step to any player, its trigger will not work. Instead of that active player receives one damage from Divine Deflection. On the second damage step Blademaster deals one damage to a cunning opponent and on trigger’s resolution it will get its earned +1/+1 counter.