. . . the dog, which you can get quite early on? I always depended on him when I used Light Magic parties. (I don't remember his name, and I can't go find him because of my stubbornness in refusing to pay for MMX yet a third time.) He's being held by a gang of thugs in the woods one map down (or thereabouts) from New Sorpigal or whatever the starting town is. (Again, senior moment. I am 84, after all.) Instead of taking him back to his kennel/lair, just add him to the party.
I've completed MMX with every possible class as main character, both Light and Dark. So unless the game has been re-patched, it should be possible to win it every time.