Horses and other mounts and enclosed spaces

[haplot]

with donkeys, mules, horses and warhorses, would each of them willingly go into dark enclosed spaces and how would each of them react to combat, both inside dungeons and outside dungeons?

Is there any book / page references for them?

[Bronk]

with donkeys, mules, horses and warhorses, would each of them willingly go into dark enclosed spaces and how would each of them react to combat, both inside dungeons and outside dungeons?

Is there any book / page references for them?

Well, all animals are NPCs, which are controlled by the DM. By default, animals act on instinct and fight out of self preservation (Monster Manual page 268).

In order to get an animal to act against their nature, a character would need to train them and use their Handle Animal skill and/or Ride skill and/or Wild Empathy check.

The more training the animal has, the easier it is to use Handle Animal and Ride. Warhorses are highly trained in combat, and it would be easier to convince them to do something like what you're describing. Same with other Warbeasts (MM2).

[Thurbane]

On this topic, the gear section does say this:


Unlike a horse, a donkey or a mule is willing (though not eager) to enter dungeons and other strange or threatening places.