From D&D Wiki
This is some stuff I wrote about riding other characters after making the Toswars and Quricke races
Obviously, like normal, you cannot move away from your mount without dismounting and when they move you move with them but they are (probably) not built to be ridden, so you need to think and say where you are on them as this affects who you can reach and who can reach you so you need to talk to the DM about how you can move on your mount, maybe you can only be in a specific space, maybe you can move but it counts as if you are on difficult terrain or it requires an acrobatics check, or maybe it depends on where on them you are trying to move to.
You also need to consider if you need to be holding them with your hands as that would restrict the weapons you can use and the spells you can cast and if you do need your hands, you need to know what happens when you do an action that uses your hands like do you immediately fall or can you make an acrobatic check to hold on in which case the DM needs to make a DC and know how often you need to make a check which could be from a max of one per turn to one for each action, bonus action, reaction and weapon attack (if you have multiattack)
These are important questions so if you are planning to ride someone (or be ridden) a lot you should spend some time with the DM figuring out the answers.
These two subclasses were made for specific characters
Beginning at 6th level, when you would add your bonus rage damage to an attack you also add it to the attack's attack roll
While raging you are immune to fear and charm
Always resistant to physical and while raging you are resistant to all damage
Collage of Skills
Learn 3 more skills
Knowledge points. Have 1 per 3 levels. Spend 1 to gain proficiency. Spend 2 to double proficiency. Spend 2 for advantage on 1 ability check. Lasts 10 min. Refill after long rest.
Can use bardic inspiration on own ability check
Treat rolls of 2-9 as 10 for ability checks (without disadvantage)
Like rogue thief but more so, and has ways of dealing with magic
Doesn't do much damage instead they trip, disarm, knock prone, grapple, taunt, distract, illusions so on so forth
So it is all about focusing on making good decisions for others, whether that is because they are animals, from other planes or it is a group of people
INT and CHA
You have d4 hp but you can get hp through your own squad HP
And link mage
Squad hp; Your charisma gives the whole group hp because of willpower and moral
Pet swarm; damages by dex save or 1d4 damage per 10 Hp the swarm has, success for half damage. If the target has evasion or similar, instead of the normal effect the target has resistance to the damage.