If a mage or spellsword took the proficiency riding:horse, would they be able to move in the same round as they are casting a spell (non-concentrated).
Is it you have no control over your mount, so if you are riding in a group your horse just follows all the other horses or is it you need to bring your mount to a stop as the bouncing is getting in the way of your hand-gestures or whatever?
Say if you were atop a dwarven construct or an elephant, would the movement of the machine distrupt your magic or would you be able to cast while sitting down on them?
I can't speak for the actual rules of the game, but in my own game I did about what you're describing: having the riding proficiency lets you ride on a horse and cast spells. If you're a passenger on a mount being led by someone else, you can also cast freely even if you don't have riding.
The requirement that spellcasters remain stationary is a relatively important part of the balance between casters and non-casters in ACKS. It prevents, for instance, a caster from hiding behind a wall until his initiative, then moving out and blasting the bad guys with a fireball. Instead the caster has to sit in the open as an easy target until his spell goes off.
So that argues against allowing casters to cast spells while on a moving horse. On the other hand, it seems like a caster ought to be able to cast spells while on a ship, even though the ship is moving. What about movement in between horse and ship - in a howdah on the back of an elephant, say?
To resolve these questions, I concluded that a caster cannot move and cast spells if the movement is under his direction and occurring based on his initiative roll. So I would allow a caster to cast from a howdah on the back of an elephant provided he wasn't the driver of the elephant.
But there are other circumstances to consider as well. What if the mount rears up? What if the mount attacks? What if the mount jumps, or changes direction? All of that should interrupt casting.
A caster on a moving animal or vehicle can declare he is casting a spell provided he is not controlling the animal or vehicle and provided the animal or vehicle has its own (or driver's own) initiative roll. He must have the Riding proficiency (if on an animal).
A caster casting from a moving animal will lose his spell if the animal charges, runs, attacks, suffers damage, or abruptly changes direction.
A caster casting from a moving vehicle drawn by animals will lose his spell if the animals drawing the vehicle charge, run, attack, or suffer damage, or if the vehicle abruptly changes direction.
It prevents, for instance, a caster from hiding behind a wall until his initiative, then moving out and blasting the bad guys with a fireball. Instead the caster has to sit in the open as an easy target until his spell goes off.
This is a bit off topic from the original request, but in our game we've found this out-in-the-open-ness makes it extremely hard to actually cast spells in the size of combats we get into. because my 5 players have an average of 3 henchmen each, they tend to attract enough attention that several attackers will go before a mage and one of them is bound to hit. similarly, an enemy spellcaster is almost guaranteed to be interrupted in the party knows there's a spell being cast.
The followup question, then, is if there's anything a mage's meatshield henchman can do to help them get a spell off? we often have a situation where the corridor is too narrow, and all the spaces for front line fighting and 2nd rank spearing are already taken. Could a shield bearer focus their entire turn on helping to deflect incoming arrows? SHOULD they be able to? that would certainly dramatically increase the number of fireballs cast.
Great question. I think you can allow a shieldbearer to use the "defend" action from Domains at War to gain a +4 bonus to AC versus arrows and one other stationary character. I typically also rule that having characters in between the target and the shooter counts as cover for the target, typically imposing a -2 penalty to hit.