2 knights go on a journey , fight giant green caterpillar-is creature. Eventually they fight bats

Hello all! I’ve been having this on my mind for quite the time now, but I’ve had a fading memory of an animated movie where there are two knights that go on a quest that I can’t remember what for, but I just remember that the knights were talking at a balcony and I remember one of the knights being sad, maybe due to his inexperience and need to improve. I know that these two knights venture on to kill an obese slimy monster. I believe it shot green slime out at the knights but eventually it was defeated. Later on the knights fight a large swarm of evil bats. Please, can anyone help me track this? Thanks!