Cooperative Bound

Starting at 1st level, the steed gains the ability to coordinate with its rider to a superior degree. When serving as a controlled mount, the rider can direct the steed to take any action other than multiattack listed under their actions as a bonus action.

When serving as an uncontrolled mount, the steed gains the ability to swap initiative with their rider after rolling initiative if both creatures are willing.

Swift Prancer

Starting at 2nd level, the steed can pass through tight gaps with adroit agility and does not need additional movement to move through spaces it has to squeeze through, though if it ends its turn in a spot too small for it, it still considered squeezing.

Additionally, the steeds movement speed increases by 5 feet. It increases by 5 additional feet to 9th, 13th, and 17th level, as shown on the class table.

Inseparable Pair

Starting at 3rd level, the steed gain advantage on any saving throw or ability check to resist forced movement. In cases where it subjected to forced movement, the rider automatically succeeds their save to stay mounted.

Additionally, if the rider would be knocked off the steed by forced movement targeting the rider, the steed can use their reaction to move up to their movement speed to the location the rider would be knocked. If the steed can move to the new position with the reaction, the rider stays mounted.

Ability Score Improvement

At 4th level and again at 8th, 10th, 12th, 16th, and 19th level, the sidekick increases one ability score of your choice by 2, or the sidekick increases two ability scores of your choice by 1. The sidekick can't increase an ability score above 20 using this feature.

Multiattack

Starting at 6th level, when allowing a controlled mount to take an action, it take a multiattack action if it has one. If the Steed does not have a multiattack action, it gains one, allowing it to use an combination of two of its actions (if it has multiple actions), or take its lowest damage attack twice.

Assisted Assent

Starting at 7th level, the steed excels as picking up their rider with minimal effort. Mounting the steed requires only feet of movement, rather than half of the rider's movement.

Divided Damage

At 10th level, when a steed and its rider take damage from the same area of effect spell, ability, or effect, they split the damage between the two of them rather than both take the full damage.

Steed's Bond

Starting at 11th, the steed can form a powerful build with another creature, most typically its rider, during a long rest. The steed can then telepathically communicate understanding with that creature while within 5 miles of it on the same plane.