I saw this (probably B) movie on TV in the early 90s, so it's probably an 80s movie.
The male hero completes a journey consusting of 3 (maybe more) quests, in a medieval fantasy world, probably to save a princess. I remember 2 scenes:
1. The hero sits at a table on a mountain with an antagonist who won't let him pass. The hero fills up 2 cups and tells the antagonist that one is poisoned. The antagonist plays the game, drinks one cup and dies. The hero tells him that both cups were poisoned and that he is immune to the poison.
2. The hero successfully fights giant rats in a cave.