#steps of combat

[mtgtutorials]

During the Declare Blockers step, if you declare blockers (or no blockers) and your opponent plays an instant or flash creature, can you change your blockers?

Short answer: No, you can’t.

Longer answer: Combat is broken up into several different steps, and players have the opportunity to play spells or use other effects in between each step. Once you’ve moved to a new step, it’s too late to go back in time and change your decisions from previous steps. 

For a quick primer on the steps of combat, I recommend checking out MTG Tutorials #13: What Are The Steps Of Combat?

[mtgtutorials]

Is it possible to block-sacrifice? Say my opponent is attacking with a 3/3 creature and I'm blocking with a 2/1 Corpse Hauler. Can I use the Corpse Hauler's sacrifice ability before it dies?

Yes. Much like the rest of your turn, combat doesn’t happen all at once, but rather is made up of several steps. You have the opportunity to cast spells and activate abilities during each step, before the next step begins.

In particular, you certainly have the opportunity to sacrifice Corpse Hauler to its ability after it’s declared as a blocker but before combat damage is dealt. (Be aware that if you do this, the Corpse Hauler itself won’t deal combat damage to the creature it blocked.)

For more on the steps of combat, check out:

MTG Tutorials #13: What Are the Steps of Combat?

EDIT -- mrfb said: 

Will the 3/3 creature deal damage to the blocking player?

Not unless it has trample. It's still considered blocked, because a creature was declared blocking it this combat.

[mtgtutorials]

Hi. I am running a vampire deck using things like Blood Artist and Bloodthrone Vampire. I am wondering how blocking and bloodthrone keeper’s sacrifice ability interact. Can I block with one creature, sacrifice it with bloodthrone vampiure and still get the block usage out of it. For instance I am running a Sorin in my deck and want to know if I can chump block a big creature with the 1/1 lifelink flyer he produces AND sac that 1/1 flyer before the damage resolves, boosting the bloodthrone and possibly using the interaction with Blood Artist, and still get the block usage. And when attacking I am unsure of how this might work. For instance if I was swinging in with a creature and they chose to block that creature instead of my bloodthrone could I respond by sacking and buffing my bloodthrone. I would also appreciate any tips or knowledge you have on how sacking abilities interact during attacking/blocking and what have you. Thank you! Love the blog, always a big help. 

— youdontknowshitaboutcats

Thanks for the kind words!

You have essentially three opportunities to use spells or abilities (including sacrificing creatures to Bloodthrone Vampire) during combat before damage is dealt: beginning of combat/before attackers (i), before blockers/after attackers (ii), and after blockers/before damage (iii). Depending on which of these times you sacrifice your creature, you will achieve a slightly different effect.

If you sacrifice your creature during the beginning of combat or right after attackers are declared, you will not be able to block with the sacrificed creature (because it's not still around when blockers are declared).

If you block with your creature, then sacrifice it before combat damage, the creature it blocked is still considered blocked. If that creature doesn't have trample (and it's not blocked by any other creatures) then it won't assign any combat damage this combat. If it does have trample, it will assign all of its combat damage to the defending player/planeswalker (because it will trample over all of its zero blockers).

The steps are the same when you're attacking. If you sacrifice your creature after it's been blocked but before combat damage is dealt, Bloodthrone Vampire will get larger before it deals or receives any combat damage.

Hope this helps. Let me know if you still have any questions.