I'm going to be playing this AP in a bit and I'm considering playing a hobgoblin fell rider/beast rider. Is this AP okay for cavaliers?
There's a Cavalier class that can have hounds. I'd go with that one. Because you have several dungeon environments and the snow terrain makes it impossible to charge enemies even with a steed.
I'm considering taking the Fell Rider archetype so I get trample and bonuses to that instead of charge, so I can probably minimize the drawbacks of being unable to charge
Even so, you still have dungeon and indoor environments on multiple occasions. Probably the only cavalier that would have a chance is a halfling/gnome cavalier on a riding dog, as they can maneuver in that environment more easily. Mostly, the cavalier tends to end up missing out because the mount isn't usable in many circumstances. (It's why most Paladins tend to go with a bonded item.)
Yep what Tangent said. They work for the first half of book 1. the first third of book 2, not in book 3 at all, first half of book 4, half of book 5, I haven't read book 6.