Mounts

Mounts are a new feature in Diablo IV, added for the very first time in the Diablo series.

Lore
Horses were used as mounts by ancient nephalem. Millennia later, their human descendants still retain the practice.

In-game
Mounts are used as a means of transportation for traversing across long distances in the open world. Mounts can be customized via their armor, saddle, and can have trophies dangling from them (said trophies including severed heads). However, this customization is aesthetic only. Different types of mounts exist, including demonic horses, flayed horses, and dead horses. Mounts can be obtained in a variety of ways, such as by completing puzzles, finding hidden locations, or slaying certain monsters. The mount's speed can be altered by collecting different types of horseshoes.

All character classes have special dismounting attacks that allow them to perform a special offensive action the very moment they leap off their mounts. If a monster attacks the mount, the player is forced to dismount.

Development
The developers decided against jousting or fighting from horseback, as it didn't feel true to the series.

Trivia

 * Horses were used as mounts by ancient nephalem.