Rinse, peel (if not organic) and roughly chop horseradish and ginger root (into about ¼ inch/½ cm pieces).
Peel and roughly chop garlic cloves.
Remove tops, membranes and seeds from chile peppers (or leave the seeds and membranes in a few of them for extra heat).
Slice onion into rough pieces.
Optionally, pulse all ingredients in a food processor a few times.
Add ingredients to a quart/liter sized mason jar.
Top with vinegar or ripe kombucha. Fill all the way to the top. Secure lid tightly.
Shake jar vigorously every day or so.
After 30 days, strain out the liquid into a bottle. You now have fire cider! Store in a cool, dry place (refrigeration is optional).
You can use the leftover solids to flavor other dishes, or to add to the compost.