How does maneuvering and counter-attacking work for mixed Aerial/Ground combat?

Question

I'm running a 5e campaign with a group of three PCs. One PC rides a Griffon and I typically struggle to effectively run combat when she is in the air and the other PCs are on the ground. She spent several quests working toward this goal and it's actually lead to some very fun role-playing. I'm just trying to make combat less clunky.

Here are my specific questions:

1. How long would it take for a flying creature to make a pass at an enemy? (either diving for a melee strike or shooting with a bow from the flying mount)

2. What counter-strike abilities would the person on the ground have? Must the bide initiative and take a swing as the person is diving?

3. What modifiers would be appropriate in this case?

My thinking is a person on a flying mount should have a substantial advantage vs. those on the ground. However, I think that the ground enemy should have some recourse if attacked by someone on a flying mount.

Answer 1

Looking at the rules for mounted combat (PHB p. 198) and flying (PHB p. 191), you should bear the following in mind:

• The griffon acts and moves on the player's turn, and can only take the Dash, Disengage and Dodge actions.
• If the griffon falls prone or has its speed reduced to 0, it stops flying and falls to the ground.
• If the griffon is forced to move, or if something knocks the rider prone, the rider must make a DC10 dexterity save to stay mounted.
• If the griffon provokes an opportunity attack, the rider can be attacked instead.

Attacking the rider of a mount doesn't have any special penalty. Given all that, the RAW answers to your questions are:

1. The griffon can move as much or as little as its rider wants on each of its rider's turns. If the griffon Dashes, it can move a total of 160 feet in a turn.
2. A creature can take the ready action with the intent to strike the griffon or rider as soon as they are in range. Note that if the griffon is moving out of range without Disengaging, it will provoke an opportunity attack that can be made against the rider. Any spells or abilities that reduce the griffon's speed to 0 or knock it prone will cause it (and the rider) to fall to the ground, so they are also good options.
3. A character riding a mount doesn't gain any defensive advantage. There is no penalty for attacking the rider of a mount, assuming the rider is also within the attacker's reach.

Things do get much worse for the creatures on the ground if the rider has the Mounted Combatant feat, of course.

You can also set up encounters where the enemies have cover, or can retreat into spaces too confined for the griffon to fly or enter. On the other hand, if the player enjoys having their character fight from griffin-back, then you shouldn't take that away from them. You can also add some flying enemies to their encounters.

Answer 2

The person on the flying mount has a pretty big advantage in this scenario. The only real recourse a defender has is to ready an action to attack the mount (or mounted person) as they are coming in.

To answer your specific questions:

1. Use the mount's fly speed. The griffon has a fly speed of 80 feet.

2. Ready an action to use her reaction to attack (perhaps grapple or shove) the mounted combatant, in an attempt to knock them from their mount. Otherwise, if available, use ranged spells on the defender's turn in initiative. Other methods of combating the griffon include reducing its total speed to 0 or knocking it prone; both result in it ending its flight rather violently and taking falling damage from whatever height it was at before it fell, taking its mounted pilot with it.

3. I would probably give disadvantage to the defender on the counter-attack, based on the circumstances, but there are no hard rules to support this. Barring any other circumstances, the attack should be made as normal, unless I've missed something.