Can anyone help me with the aim order? From what I understand, I can place an aim order and either move or attack. However, according to the rules, movement removes the aim order. So why would I ever choose to place aim and then move? Also, why wouldn't I just use battle instead of placing the aim order since battle can essentially act as a "re-roll." Lastly, I believe that the aim order is not an attack, merely a modifier on an attack. (But this has caused some discussion in my household, so I would like some clarification on that one.)

You are correct that an Aim order modifies an attack, it does not allow you to make an attack; in order to use it, you must already be entitled to make an attack, and the Aim order simply converts it from a regular attack to an aimed attack. It would be difficult to understand why someone would use an Advance or Battle action if an Aim order let you make an aimed attack all by itself.

You might choose to place an Aim order and move because the order can be placed at any time during your turn (for example, after moving); notice that the Aim order is the only order that can be saved and used on a subsequent turn. You might also choose to spend the movement points on movement actions such as opening a door or chest or drinking a potion, which do not involve actually moving. However, even if there were no situation where moving an Aiming in the same turn were a good idea, the Ready action might still be written the way it is so that movement could be combined with the other orders (Dodge, Guard, and Rest).

You might choose to make a single aimed attack rather than two attacks (e.g. with a battle action) because you can choose which dice to reroll with the aim, which can potentially give you a higher probability of an extreme result than if you made two independent rolls. For example if you need a lot of range, or if you need lots of surges to trigger an effect or to overcome Fear , you might achieve better odds by rerolling only your bad dice than by making two separate attacks. Any resources you spend on the attack (such as fatigue, or a power potion) would also need to be spent twice in order to gain the same benefit on two attacks.

However, in normal Descent, making two attacks still ends up being significantly better than a single aimed attack almost all the time. Aim is very rarely used.

Yeah, but don't forget that a Ready action isn't the only way to get an Aim order...

Leadership in the base game, and Captain for SoB both allow you to give orders without taking a Ready action, and you can even give them to someone else (Captain gives orders to everyone else), letting you setup another hero with an Aim order to use during their action.

If you use Leadership to give someone an Aim, you're giving them that instead of a Guard (or something else), so you're basically still choosing one aimed attack instead of two normal attacks.

And my suspicion is that I'd normally use Captain for a Dodge or Rest rather than an Aim, unless I'm fighting monsters with Stealth, but I've never played an extended campaign and have no plans to do so, so *shrug*.

That helps a bunch. Thanks!