How does mounted combat work?

Do you know if there is anything RAW that covers mounted combat on say, a Dragon (I'm thinking a Githyanki Knight on a Young Red Dragon)?  I feel like the dragon should still be able to breathe fire, and maybe even Rend, but I'm presuming the Knight could control/direct the mount to go where it's supposed to go.  So, does that count as the dragon being controlled or uncontrolled?  And would it work if the dragon swoops within range for an attack, say with Rend (maybe breath weapon is down), and the Knight wants to make a sword attack at the same time, but they fly back up after both?  I realize this would likely generate an Opportunity Attack, since the dragon doesn't have Flyby Attack, but would often be worth it.

There are rules for non-controlled mounts. Basically they just become a moving place for you to stand while you are mounted. They act independently of you. This is from the mounted combat section of the PHB:

In contrast, an independent mount—one that lets you ride but ignores your control—retains its place in the Initiative order and moves and acts as it likes.

There are rules for controlled and uncontrolled mounts.

https://www.dndbeyond.com/sources/dnd/phb-2024/playing-the-game#ControllingaMount

A controlled mount moves on your turn as you direct it, and it has only three action options during that turn: Dash, Disengage, and Dodge. 

An uncontrolled mount moves on its own initiative turn and can do whatever it wants. 

If youre riding a controlled mount, you can basically decide where it goes, when, and how. You can have your mount move, you do an attack, have your mount move some more, and you do another attack.

If youre riding an uncontrolled mount, the mount moves and attacks on its turn and youre just along for the ride. When initiative gets around to your turn, you can attack and take other actions, except for movement actions, unless you dismount.

If a mount is an uncontrolled mount, such as a creature you encounter in the wild, the dm may maintain control of it. 

Quote from SunIsGettingRealLow96589 >>

There are rules for controlled and uncontrolled mounts.

https://www.dndbeyond.com/sources/dnd/phb-2024/playing-the-game#ControllingaMount

A controlled mount moves on your turn as you direct it, and it has only three action options during that turn: Dash, Disengage, and Dodge. 

An uncontrolled mount moves on its own initiative turn and can do whatever it wants. 

If youre riding a controlled mount, you can basically decide where it goes, when, and how. You can have your mount move, you do an attack, have your mount move some more, and you do another attack.

If youre riding an uncontrolled mount, the mount moves and attacks on its turn and youre just along for the ride. When initiative gets around to your turn, you can attack and take other actions, except for movement actions, unless you dismount.

If a mount is an uncontrolled mount, such as a creature you encounter in the wild, the dm may maintain control of it. 

 

So, in my scenario where a Githyanki Knight rides an Adult Red Dragon mount, the Knight can only hope that the dragon decides to attack the correct target, and since the knight doesn't have any ranged attacks, it would have to try and swing at whatever the dragon tries to attack (if it could even reach it, which I'm doubtful of--I really feel they should give those guys crossbows or something).

In my actual session I ended up having the knight use its Misty Step to appear next to the party so that it could use its Silver Sword, and the dragon continued to do its own thing, just being really careful with its breath attacks to avoid hitting its "master."

It would be more ideal though if the knight had been able to stay mounted and fire ranged attacks on its turn.  I could always DM a crossbow for them, but I really feel a lot of these monsters in the MM need a ranged option by default.

I mean, if a sapient being is allowing a rider, then presumably they have a cooperative dynamic and thus the dragon will typically maneuver so that the Gith has a target in range as well.

If you are sticking with the typical lore, then as ace of rogues says, I’d see them working together. And the dragon is smarter than the knight, so it’s probably going to pick a good target.

The bigger issue would be, technically, each would go on their own initiative count, so if the dragon is just swooping in and swooping back out, the githyanki is likely left to just ready an attack meaning it only gets 1 attack (probably with advantage for being on a huge mount) instead of 3. That’s the part I would consider house ruling to let the gith get its full attacks.

Or have it go nuts with telekinesis just lifting people up and dropping them 30 feet. Or off a cliff or side of a building. It can actually be a pretty effective ranged attack in a pinch.

Quote from Xalthu >>

If you are sticking with the typical lore, then as ace of rogues says, I’d see them working together. And the dragon is smarter than the knight, so it’s probably going to pick a good target.

The bigger issue would be, technically, each would go on their own initiative count, so if the dragon is just swooping in and swooping back out, the githyanki is likely left to just ready an attack meaning it only gets 1 attack (probably with advantage for being on a huge mount) instead of 3. That’s the part I would consider house ruling to let the gith get its full attacks.

Or have it go nuts with telekinesis just lifting people up and dropping them 30 feet. Or off a cliff or side of a building. It can actually be a pretty effective ranged attack in a pinch.

 I like those ideas, but I believe it only gets one Telekinesis use per day?

Quote from sethtucker1 >>

Quote from Xalthu >>

If you are sticking with the typical lore, then as ace of rogues says, I’d see them working together. And the dragon is smarter than the knight, so it’s probably going to pick a good target.

The bigger issue would be, technically, each would go on their own initiative count, so if the dragon is just swooping in and swooping back out, the githyanki is likely left to just ready an attack meaning it only gets 1 attack (probably with advantage for being on a huge mount) instead of 3. That’s the part I would consider house ruling to let the gith get its full attacks.

Or have it go nuts with telekinesis just lifting people up and dropping them 30 feet. Or off a cliff or side of a building. It can actually be a pretty effective ranged attack in a pinch.

 I like those ideas, but I believe it only gets one Telekinesis use per day?

One cast of a 10 minute duration spell- you can use the spell on multiple targets across the duration, following the action economy outlined in the spell.

Being on an independent mount that has a massive fly speed and likes to stay far away from the fight, will be a problem for a melee rider.  They swoop in, do a breath attack or something from range, then swoop out. 

By the time its the monk's turn, they're a hundred feet from any target.

Raw, the best you can do is Ready action on your turn and prepare one melee attack when the mount swoops in.  Or get a ranged attack of some sort.

I do recall a campaign many moons ago, i played a dragon born, draconic sorcerer who spent a dozen levels searching for a dragonelle during any downtime. At level 12, the dm finally relented. Oh it was marvelous.

Cast dragons breath on the dragonelle (let them join in on the fun), and then kite around the battlefield lobbing ranged spells.

Quote from The_Ace_of_Rogues >>

Quote from sethtucker1 >>

Quote from Xalthu >>

If you are sticking with the typical lore, then as ace of rogues says, I’d see them working together. And the dragon is smarter than the knight, so it’s probably going to pick a good target.

The bigger issue would be, technically, each would go on their own initiative count, so if the dragon is just swooping in and swooping back out, the githyanki is likely left to just ready an attack meaning it only gets 1 attack (probably with advantage for being on a huge mount) instead of 3. That’s the part I would consider house ruling to let the gith get its full attacks.

Or have it go nuts with telekinesis just lifting people up and dropping them 30 feet. Or off a cliff or side of a building. It can actually be a pretty effective ranged attack in a pinch.

 I like those ideas, but I believe it only gets one Telekinesis use per day?

 

One cast of a 10 minute duration spell- you can use the spell on multiple targets across the duration, following the action economy outlined in the spell.

 Great point--sounds fun and thematically exciting, too!  :)