Well, the character of the trainer in Phantom Stallion fanfiction can be quite interesting. They bring in their knowledge and skills in handling horses, and sometimes have to face the unique challenge of the Phantom Stallion. Then there are the characters from the neighboring ranches. Their interactions with the main characters and their different attitudes towards the stallion create interesting storylines. Also, any characters who have a special gift or intuition when it comes to horses are always engaging in these fanfictions.
The Phantom Stallion himself is definitely one of the most interesting characters. His wild and free nature makes him a captivating figure. Also, the main human character, usually the one who has a special connection with the stallion, is interesting as they navigate their relationship with the horse.
The ranchers in the Phantom Stallion fanfiction can be really interesting. They have their own views on the stallion, some seeing it as a threat, others having a more sympathetic view. And there are often other horse characters that have their own personalities, like the loyal companion horses of the main character. They add depth to the stories. And of course, any mysterious characters that are introduced, like the ones who might know the secrets of the stallion's origin.