|our version of Superhorse|
Valve Software is a video game maker (Half-Life, Portal, Counter Strike) and we assume that one of your figurines referred to one of their copyright-protected games or characters. Most likely Valve uses software that routinely searches Etsy and similar sites for references to its games. Once it finds them, it issues take-down notices (possibly without considering fair use). You can push back if you feel like the notice is improper -- that is you don't believe your figurine infringes or is excused under fair use principles -- by filing a counter-notice. Etsy simplifies the counter-notice procedure and would be obligated to re-list your item once you file it. After that, Valve Software's only other recourse is to sue you. Considering the vast number of bunk DMCA notices, it is always possible that Valve made an error targeting your store.
What can you do? Unfortunately there's not much you can do to avoid takedown notices. You could remove the text references to copyright and trademarked characters in the product blurbs -- the marketing equivalent of shooting oneself in the foot. It's probably best to deal with these notices on a case-by-case basis.