I mean, the only horse in all of the game is the horses in the charioteer boss. Which is A: optional as it only grants access to a particular PvP covenant, and B: easy to miss.
Also you don't directly fight the horses normally.
@Nine I still love "Don't give up, skeleton!"
@theoutrider
One day they'll escape their stone prison behind that door
But then again this is a game series where "skeleton but hole" is a reoccurring message