Let's say we have a group of four crabs in Core or Accelerated, but I'm treating them as a mob.
One individual crab looks like this:
Stress:  (one stress box, further damage takes them out)
First things first, here's my understanding of such a monster. They can take 1 stress, which leaves them open for a blow which would take them out. So a weak, 1-stress hit wouldn't take them out, but a 2-stress hit would. Ok.
Here we have the swarm of four crabs:
Crab Swarm (four)
Stress:    
For the purposes of this question, it matters how many crabs are still alive - maybe each crab gives a bonus or something.
My questions are these:
- What happens if the swarm takes 1 stress? Does a crab die or does it just lose its "stress shield"? What would happen on the next 1-stress hit? Does it get taken out and the second crab get wounded? Or does that first one just get taken out? Would that mean the swarm has 8 effective stress?
- What happens if the swarm takes a blow of 4 stress? Is it defeated? Does it get to choose if it leaves all crabs open for defeat? Do all but one die out? Does it have 4,5 or 8 effective stress?
- How is the game changed if each crab had multiple boxes of stress, or one box of 5 stress? Does the swarm then have 20, 21 (5 x 4, plus 1 swarm takedown stress) or 24 (5 each, plus 1 final blow) effective stress?
I am interested in answers that relate to both Fate Accelerated and Fate Core.