u/Sapentine

I was playing around with a hypothetical combat today using a Moon Druid vs a smart monster with knockback. The moon druid cast moon beam and then wild shaped into a dire wolf and ended their turn.
Then I had an inspired idea. I had the monster run around the moon druid (out of the moon beam), and did their shove attack so they are pushing the dire wolf into their own moon beam. Dire Wolf rolled a one on their strength save and now they have a shitty decision to make.
They can:

• Make a con save and take 2d10 radiant damage (half on save). Then make a concentration check for moonbeam since they took damage
• Be reverted to their true form

OR

• Voluntarily drop concentration right before they are moved in

Pretty sweet move for a monster that knows what they are doing.

I've been going down a rabbit hole on this one and I can't find a clean answer, so I wanted to get the community's take.

**The scenario:** A mounted PC is in melee range of an enemy. On their turn, the mount moves away. No Disengage action for either of them. Does the enemy get an OA, and if so, against the mount, the rider, or both?

**The case that only the mount provokes:**

The 2024 OA rule triggers when *you* voluntarily move out of reach. The rider didn't move, the mount did. The rider is essentially cargo in terms of movement; their position changed as a consequence of the mount's action, not their own. On a controlled mount you use the mount's movement, not your own, which suggests the mount is the creature "spending" movement and therefore the one provoking. By this reading, the rider is never independently leaving anyone's reach and shouldn't trigger an OA at all.

**The case that the rider also provokes:**

The rider chose to stay mounted and directed the mount to move. That's a deliberate decision to leave the enemy's reach. "Voluntary" doesn't necessarily mean "I moved my own legs", it means you made a choice that resulted in leaving reach, which the rider absolutely did. Letting mounted combat grant blanket OA immunity to the rider starts to feel like an unintended loophole, even if the mount itself is a legitimate resource with real costs.

**The bonus wrinkle that broke my brain:**

What if the mount uses its action to Disengage but the rider doesn't? Disengage only protects the creature that took the action, so the mount is now safe, but does that *increase* the case for an OA against the rider? One argument says yes: the mount's protected movement makes it clearer that the rider is the one "voluntarily" departing. But that produces a perverse outcome where the mount spending its action to Disengage somehow makes things *worse* for the rider, which feels wrong.

The cleaner ruling is probably that the mount Disengaging is purely a benefit (protects the mount only), and the rider's OA exposure doesn't change based on what the mount does with its action.

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Curious where people land on this. Is the rider always insulated from OAs while mounted, or does staying in the saddle while your mount gallops away count as a voluntary choice to leave reach?