Cover turkey carcass in water; boil. Reduce heat & simmer 2+ hours (the longer you simmer, the more flavor). Pull off loose meat and save (about 2 cups). Strain mixture to save broth for soup, discard bones.
Make wild rice soup per package directions. I like to use extra turkey broth instead of water to give it extra flavor.
In soup kettle over medium heat melt butter; add onion, celery, garlic, and carrots until transparent, about 5-7 minutes.
Reduce heat and add in flour; cook and stir for 2 minutes.
Gradually add in broth; stirring constantly. Add seasonings while bringing to a boil; cook for 1 minute.
Reduce heat to low; add wild rice, turkey, and sherry and simmer 20 minutes.