Was or were on medieval time?

https://preview.redd.it/2u2ykmuy1xjg1.png?width=1649&format=png&auto=webp&s=b6c178ac2f249406059b17c42f7cbae3d1b24f6a

I know nowadays it's common to use "was" instead of "were" for subjunctive, but was it like this in the past? (This screenshot is from a series about a knight of 7 kingdoms.