I have a new player who is just learning the game and has decided to play a paladin. Specifically she wants to use her Divine Bond to get a mount and engage in Mounted Combat. I warned her that the rules are a little complex for a beginner, but she's seriously into the whole "knight in shining armor atop a valiant steed" thing, so I decided to write her up a little guide to explain the rules and what the different feats will do and so on. But when re-reading the rules, I realized there are things I don't really understand myself.
Specifically my issue is Combat Maneuvers. Some of them, like Disarm and Sunder, seem straightforward enough, but the others are confusing, and I'd like to know if the rules have ever been clarified, or if not how you would interpret them.
Grappling: Is it even possible to grapple someone while I'm on a horse? If I do, what happens if my horse moves? Is my victim carried along with me? What if my target is also mounted? If my mount is grappled by a monster, but I am not, how does that affect me?
Bull Rush / Overrun: Who actually performs these actions, me or my mount? If it's my mount and I have feats that improve them, can I use those feats, or does my mount need them too? Some of them, like Trample, seem to apply to the mount if I have them, but others are unclear. And if it's me performing the action, does the fact that the mount is large give me a bonus to CMB?
Trip: The Core Rulebook has rules for if my mount "falls" in battle, but all it says is that I need to make a ride check to avoid 1d6 damage. I assume I'm still mounted, but do I take any penalties for being on top of a prone horse? Am I prone too, until the horse gets up?
Mounted combat is a real vague area, and there's a lot of disagreement about it on these boards. For instance, you can find several threads just on the topic of your second question. It seems like the horse is the one doing the overrun, right?, except that certain cavalier archetypes grant the humanoid rider the bonus. See the fell rider hobgoblin archetype from the advanced race guide.
The fell rider receives a +2 bonus on overrun attempts made while mounted
Emphasis mine. In this case, it's quite clear that the fell rider id the one getting the bonus, not the mount, but it only applies when mounted, so he must be performing the overrun. But then does he need Improved Overrun to not trigger an AoO? Does the horse?
Just to decide what you think it should be and clear it with your paladin first because there's not going to be anything in the RAW that solves these problems for you. My advice would be to make it so that either the horse or the rider (my personal preference) uses their CMB and bonuses to overruns and bull rushes. If you're grappled and want to drag someone, use the drag rules, ignore the fact that a horse is involved. If a monster grapples your horse, how do you think it should affect you? If the horse gets tripped, decide whether you get tripped too. None of this will unbalance your game, regardless of how you rule it.
