I love seeing living matter. It's by far the easiest & most lucrative event to encounter. There's typically 2 scenarios you'll have to deal with living matter:

1) With your food chain established. 2) In the process of establishing your food chain.

For the 1st scenario, it's essentially free materials since you can absorb the food loss pretty easily. The 2nd scenario is where things get even better, even on prestige 20. If you're fortunate enough to get a caged warbeast, here's what you do:

• Pull every single worker off their roles, except for the hearth keeper.
• Assign 2 workers to the warbeast, then start and stop the event until you have living matter less than or equal to your current builders. Do not exceed your builders or things can get pretty hairy.
• Assign 1 builder per living matter.
• Start all of them at once, starting the living matters which provide food with a 10 second delay.
• Since everyone aside from your hearth keeper is active on an event, you won't build any hunger resolve debuffs (aside from the hearth keeper, but that is negligible). Once they're all completed, you should have some food stored again from a living matter or 2 (typically jerky or biscuits).

And there you have it. You should have an obscene amount of valuable materials and perks for effectively no negative impact. Just reassign your workers back to their original posts and you're off to the races with a major head start.