Inspiring unicorn vs shock

Question

I’m fairly new to Magic and still learning but got the basics.

My problem is as follows.

My friend person A : white deck (basic starter)
Me person B : red deck (basic starter)

Scenario
Person A declares attack with Inspiring Unicorn “when this declares attack each creature you control gains +1/+1 until end of turn” alongside another generic 2/2 creature.

Person B casts an instant, Shock, before declaring blockers, then proceeds to block other creature with 2/3 creature.

Now this is where I was confused as I thought shock would resolve first killing the unicorn before it could apply its ability or am I wrong?? As person A said they were right and the unicorns ability resolved first as he declared an attack so gains the stat increase before shock so shock would be useless.

Answer 1

Once person A declares attackers, the Unicorn's ability triggers, and a Shock won't help to stop it. However, if you cast Shock in reaction to the trigger (of course, it's better to cast it before the combat phase), it will resolve before the Unicorn's ability resolves, and will hence kill the Unicorn. I think that person B cast it 'too late' but it's hard to tell; 'before declaring blockers' can be during the remainder of the declare attackers phase.

However, even without the Unicorn around, the ability still resolves, and the other attacking creature will get the +1/+1 bonus. See Does an ability resolve if the source of the ability leaves the battlefield? for more details.

Answer 2

'Before declaring blockers' can refer to 3 point in your scenario :

1. At the beginning of combat before person A can choose wich creatures to attack with. The shock can kill either of person A creatures, probably resulting in person A not attacking.
2. In the declare Attackers Step, in response to Inspiring Unicorn's ability. Shock can either kill the Unicorn but the ability will still resolve, or the second creature.
3. In the declare Attackers Step, after the resolution of Inspiring Unicorn's ability. At this point it's too late for shock.

Most player would only consider case 3 as 'before declaring blockers', preferring 'beginning of combat' or 'in response to ...' for case 1 and 2 respectively.

Another thing to consider is that person A probably initiated the scenario by saying something like

I attack with whose two 3/3

Not leaving person B the chance to respond in the beginning of combat step. Taking shortcuts is fine and documented in the section 724 of the rules, including this rule

724.2b Each other player, in turn order starting after the player who suggested the shortcut, may either accept the proposed sequence, or shorten it by naming a place where they will make a game choice that’s different than what’s been proposed.

So don't be afraid to refuse the shortcut and be clear to when you want to act.

Answer 3

To really be as clear as possible, let's go through the full sequence of steps outlined in the game rules:

1. Combat begins.
2. Players get priority.
3. Player A declares which creatures are attacking.
4. The unicorn's ability goes on the stack.
5. Players get priority.
6. Player B plays Shock, which goes on the stack on top of the unicorn's ability.
7. All players pass priority, and Shock resolves.
8. The unicorn dies.
9. Players get priority.
10. The unicorn's ability resolves. The other attacking creature is now 3/3.
11. Players get priority.
12. Player B declares blocks.
13. Players get priority.
14. Combat damage is dealt.
15. Player B's 2/3 blocker dies, while player A's 3/3 attacker survives with 2 damage.
16. Players get priority.
17. Combat ends.

You may have noticed that players "get priority" a lot. Priority is the official game term for having a generic opportunity to "do something". Every time players get priority, they each declare, one at a time, in turn order starting with the player whose turn it is, whether they are doing anything, and what they are doing. When all players pass, the top thing on the stack resolves, and then players get priority again. When all players pass and the stack is empty, then the game moves on to the next part of the turn. Every time players get priority, any abilities that have triggered go on the stack, and state based actions such as creatures dying from damage happen, before the first player actually gets priority.

In practice, the strict formal process of priority is rarely followed. Instead, it's usually assumed that players pass most priorities when it's not their turn, until a player interrupts to state they're doing something.

Back to this specific situation, Player B can cast Shock at any of the times when players get priority.

• At step 2, you could kill the unicorn and prevent it from doing anything. Player A would not yet have declared attacks, however, and could therefore choose to not have his 2/2 creature suicidally attack into your 2/3 blocker.
• At step 5, you can kill the unicorn, but it's too late to stop its ability from happening. The unicorn dies, and Player A's creature is committed to the attack, but it will get the +1/+1 if you don't do something else to stop it.
• If you instead passed step 5, steps 6 through 9 wouldn't happen. At step 11, the next available priority, it is too late to kill the unicorn with Shock.