So I came up with an awesome idea for a character to role play but I'm having one issue to think about while creating it. The thing about the character is that it is two separate characters who function as one inseparable duo. The way the two characters function is that one is a large bodied combat based class who focuses on dealing damage and performing more physically based tasks. while the other character is frail and very week, focusing more on magic being based on a caster class. The way the two characters actually interact is more on the level of a symbiotic relationship. The two characters move as one body with the caster riding on the back of the combat character using a special harness to stay mounted on him. What I actually have questions pertaining to are feats that would work well to make these two characters synergies well with one another, as well as classes that would be fun to combine. Any suggestions would be appreciated.