Magic the Gathering: counters and attacking, help?

Question

Scenario: I have 3 black creatures up, the first one is a 3/3 because its power and toughness is based on having other black permanents , the second one is a 1/1 with a +1/+1 counter, the 3rd is a 1/1.

Q1: I choose to attack and an instant is played, by the opponent, it destroys the 3rd creature, bam. Opponent has no blockers. Now i have 2 black permanents up. Will the first creature still have the 3/3 power toughness for that turn of attacking?

Q2: Same thing with a twist, but this time the instant is taking away the +1/+1 from the 2nd creature, will that creature still have the 2/2 when it attacks?

Thanks in advance.

Answer 1

For a short answer, no to both of your questions.  

For a longer answer as to why, there are numerous steps to the combat phase.  Basically:

Combat Phase

1. Beginning of combat step - instants and activated abilities may be played

2. Declare attackers step - instants and activated abilities may be played

3. Declare blockers step - instants and activated abilities may be played

4. Combat damage step - This is where damage is done and placed on the stack regardless of whether creatures are removed from play at this point.  Instants and activated abilities may be played

5. End of combat step - instants and activated abilities may be played

Depending on what step your opponent plays his instant (most likely before combat damage step), in the first example, your third creature would die before combat damage and would therefore cause your first creature to be 2/2 before the combat damage step.  In the second example, again your opponent will likely take away the +1/+1 counter before the combat damage step reducing your second creature to 1/1 before the combat damage step.

The 3/3 creature gets its power and toughness based on other permanents which is defined as a characteristic-defining ability.

402.8. Abilities of an instant or sorcery usually function only while the object is on the stack. Abilities of all other objects usually function only while that object is in play. The exceptions are as follows:

402.8a Characteristic-defining abilities function everywhere, even outside the game.

405. Static Abilities

405.1. A static ability does something all the time rather than being activated or triggered. The ability isn’t played—it just “exists.” Such abilities apply only while the ability is on a permanent in play, unless the ability is covered by rule 402.8.

405.2. A characteristic-defining ability is a kind of static ability. It conveys information about an object’s characteristics that would normally be found elsewhere on that object (such as in its mana cost, type line, or power/toughness box). Characteristic-defining abilities function in all zones. They also function outside the game.

405.2a A static ability is a characteristic-defining ability if it meets the following criteria: 1) It defines an object’s colors, subtypes, power, or toughness; 2) It is printed on the card it affects, it was granted to the token it affects by the effect that created the token, or it was acquired by the object it affects as the result of a copy effect; 3) It does not directly affect the characteristics of any other objects; 4) It is not an ability that an object grants to itself; and 5) It does not set the values of such characteristics only if certain conditions are met.

Answer 2

Q1. No...the instant happens instantly.

If it removes the 1/1 creature the 3/3 will become a 2/2 instantly if it loses that extra from you losing a creature.

Q2. The creature that lost the +1/+1 would become a 1/1 instantly.