How would you create a reverse mount character?

[narrator667]

I'm a level 2 Lizard-folk duel fighter running Out of the Abyss, my DM is willing to talk to me about letting Stool be my cavalier and use a shield and lance as long as I find the time to train him. I'm thinking of going Champion for Protection fighting style. But is there anyway I can keep Stool out of harm's way while keeping him active in combat? Party Barladin plans on upping his ability to add Temp HP and our Cleric will be able to add Temp AC, so it'll be a group project, but I don't want to revolve the whole party around it.

[MagneticKitty]

Oath of redemption tortle paladin. You can choose to take a hit for someone and able give them advantage on dex saves.. and your aura helps those in it. You also have healing and protection fighting style

[narrator667]

Oath of redemption tortle paladin. You can choose to take a hit for someone and able give them advantage on dex saves.. and your aura helps those in it. You also have healing and protection fighting style

I don't think you understand. I already have my race, fighting style, and class for at least the first two, now three levels. I still have 17 levels worth of my current Lizardfolk along with the level 0 Mushroom-folk. I've been thinking on whether Stool should go for Cavalier Fighter or Colossus Slayer Hunter Ranger to help with either giving him advantage while he's on my shoulders or traversing the under dark and dealing with drow.