Cyberzombie said:
I'd say you'd have to have wild empathy and speak with animals at a minimum before you could even try to get a horse to spider climb. And even then it'd probably kick you in the nuts when it found out what you wanted. And you'd deserve it.
I'm not even sure that would suffice.
One, almost all horses are shod, and this means their hoves aren't free per the spell's requirement for "free hands" (since the consensus seems that hands = hooves, even though I don't believe that for a second).
This is the real killer for me. I would require that any horseshoes be removed prior to using spider climb.
--------------------------------
I have a tough time visualizing how a horse is going to get both its forelegs and hindlegs up on the wall. Just "walking up the wall" isn't going to work.
I can't even begin to imagine how it would work for a ceiling. (I have a vision of the horse snapping it's rear legs off at the fetlocks.)
Next, the mage had better have Eschew Materials, because the horse isn't going to want to eat bitumen and a live spider. No, I can't see that at all.
Next, I don't like the "if a spider can spider climb, so can a horse" argument. Spider are lightweight. Big spiders are magical beasts and it is logical to assume that a part of that magic allows them to climb like a normal spider despite its size. Horses are neither of those things. Even a magical horse wouldn't logically have any of that magic devoted to climbing like a spider.
Next, I don't like the wolf or even bear comparisons. Their legs aren't built the same way at all as a horse's leg is built. Many people have seen dogs, wolves, or bears in person or on video trying to go up a wall or tree. I have seen video of a bear making it quite a ways up a tree. Never for a horse, that is, they aren't trying to get
up into the tree. A horse might try to jump a low wall, or even use its forelegs to smash a fence, but that isn't the same thing (a horse smashing a fence has to rear up on its hind legs). I can see a horse up on its hind legs (as noted earlier) in an attempt to reach leaves or fruit, but they aren't going up the tree trunk.
It's only a second level spell. It would seem that it should be restricted to Medium size creatures. Yes, I am fully aware the spell doesn't say that. It should, though.
OTOH, I might allow an unshod horse the spell to receive a climb bonus on steep grades without special tricks or training, provided the spellcaster can get the horse to eat the components (somehow).