Mounted Combat
I had not really thought about mounted combat until I came across the axe beak while preparing for Rime of the Frostmaiden. I guess it made me think of the Tauntauns from Empire Strikes Back and suddenly I wanted to make a character who could fight from the saddle. This of course took me down a rabbit hole to learn what I could about the subject.
The Basics
Just like a swim-speed streamlined underwater combat, mounted combat has been made simpler in D&D 5e. All that is required are a willing creature that is at least one size larger than the rider and has an anatomy that allows for a rider.
It takes half the character’s movement to get into the saddle. You can control the mount or allow it to act independently. An intelligent mount will act on its own. A controlled mount only has three actions that it can take which are Dash, Disengage, and Dodge. Any opportunity attacks provoked by the mount’s movement can be directed at the mount or the rider (attacker’s choice).
This is relatively simple. No damage bonuses or reach bonuses from being on the back of a mount. I would think that there would be some kind of bonus but when it comes to 5e it seems the simpler the better.
Feats
Mounted Combatant does add to the advantages of being on a mount. First, you get advantage on melee attacks on any creature that is smaller than the mount you are on. This is important if you have a small character using a medium mount then the advantage only works on other small opponents. Second, you can redirect attacks at your mount to be made at you. And third, any attacks that provoke a Dexterity saving throw cause half-damage when failed and no damage if succeeded. The first part of the feat gives you an attack advantage and the latter help to protect your mount from being hurt. These defense abilities are useful when you have more hit points than your mount in later levels.
Due to the way it is worded, and other supporting evidence, Charger does not work with a mount. This is unfortunate because a charging mounted combatant is kind of iconic.
Shield Master works well with mounted combat (and most other melee combats as well). This will give you a chance to use your bonus action to shove opponents away from yourself and your mount. The advantages added to Dexterity saving throws will make it hard to cause you or your mount damage.
Note: The way mounted combat works gives no advantages to fighting from a Broom of Flying (sorry Harry Potter fans – I was disappointed to see this as well).
Weapons
The lance is the weapon of choice for mounted combatants. The biggest problem with the lance is that it is useless when not mounted. It suffers from disadvantage if your target is within 5 feet of you. Using your mount’s movement and Disengage action to your advantage will allow you to put enemies at a range that will nullify this weakness.
Another choice is to make a mounted archer. Your mount could keep you out of melee range of your opponents while you rain arrows or bolts down on them.
Tactics
Using your mount’s action to disengage will allow you to stay mobile during combat. Your mount will most likely have a greater movement speed than you so will be able to move around the battlefield and keep your lance in play for attacking opponents.
If you want to keep your distance then using your mount to move and Dash while you either cast spells or shoot arrows would be the best way to accomplish that.
Character Classes
The most obvious character class choice is the Cavalier subclass from Xanathar’s Guide to Everything. There are some nice features that come along with the Cavalier which will maximize working with a mount. The issue is that you will be spending quite a bit of money on replacing your fallen mounts. Combat is extremely deadly to your average mundane beast after about 3rd-level. There will be quite a few dead steeds in the wake of your mounted combatant.
If your character is small then being a Ranger Beastmaster would allow you to ride your summoned companion. This works for Beast of the Land and Beast of the Sea but not Beast of the Sky (since it is a small beast). This is a very good way to have a mount that scales with your character.
Multiclassing to get at least three levels of Fighter and then going Ranger would allow you to get the best of both classes. It would not be until 6th-level that the build would be doing the basics and you would have to wait to get your extra attack. The good news is that many of the Beast Companion’s abilities are buffed by your character’s Proficiency Bonus which is unaffected by multiclassing. The Beast Companion’s hit points are unfortunately are decided by your Ranger level.
Paladins get Find Steed and Find Greater Steed which solves the problem of finding a mount. Your Paladin would have to pick up the Mounted Combat feat to maximize the effectiveness of this spell, but they would be able to accomplish this by 5th-level when Find Steed becomes available. Going Paladin would not delay your extra attack and you would not have to worry about getting the skill of Animal Handling since the steed is magical.
Fighting Styles
The fighting style of Dueling would allow you to do extra damage with a lance while mounted and still have a shield (this would mix well with the Shield Master feat). Interception will also help protect your mount from damage, but you will need to be wielding a shield. This would also pair nicely with the Shield Master feat. Multiclassing would allow you to pick up both fighting styles at a relatively low level. You would have to weigh the advantages and disadvantages of such a build.
If you are going with a mounted archer then you will want to grab Archery for that +2 bonus to attack.
Useful Spells
For non-magical steeds, having access to spells such as Speak with Animals and Animal Friendship would be very useful but unavailable to a straight Fighter/Cavalier. Speak with Animals lasts for 10 minutes and is a non-concentration spell that is first level and has the ritual tag. Awaken would be very beneficial to make your mount even more useful. This 5th-level spell is available to Bards and Druids.
Race
None of the races lend themselves to being a mounted combatant except the Variant Human and Custom Lineage. The key is the Mounted Combatant feat and the Animal Handling skill. Choosing a small race opens up the Beast Master Companion to be a Ranger’s mount. This does make it hard to get advantage on attacks since it only works with other small creatures.
Conclusion
In the right campaign or one-shot, a mounted combatant could be a lot of fun. Being able to move around the battlefield with a lance and shield would be fun, but having to leave your mount tied up outside the dungeon would be kind of annoying.
A build would have to take into account either working with an animal/beast or with a magical mount. Most builds that I envision would not come online completely until after 5th-level, so you’ll have to have a plan.
So, what did I miss? Have you made a mounted combatant and how did it go?