How to find companions (that you already have) in the sales
Because Howrse doesn't have a sales filter for companions yet
Step 1:
Go to the collections tab to find the companion you're trying to find.
Step 2:
Once you've found the companion, right-click on it and open the image in another tab.
Make a note of what it says in the tab. You'll need it.
Step 3:
Go to the horse sales.
And now we start messing with the url! Copy and paste this after the url: /?compagnon=
(Ignore the double // it still worked even with it but it's not necessary.)
Step 4:
Now you need the name of the companion as shown in the image file you opened earlier. Add that to the url. In this example I'm looking for the Screaming Ghost companion so goes here will be different depending on which companion you're looking at.
Step 5:
Press enter and look at the sales results. Usually you'll find horses that have the same name as the companion you're looking for. Check a few sales and see if they actually have the companion. If they do, it worked!
Like in my example, I did get a list of horses with the Screaming Ghost companion.
I did try this with a variety of different companion series and it consistently works!
