Okay. So here's a second draft of the archetype with a bunch of alterations made to it based on various comments and suggestions.
Level 3
Beginning when you choose this archetype at level 3, you gain two attributes. First, whenever you’re mounted you gain a +2 bonus to your Armor Class as well as a +2 bonus to your Initiative.
Second, you gain the ability to cast the spell “Summon Steed” once per long rest.
Summon Steed (Based on the spells “Find Steed” and “Find Familiar”)
Casting Time: 10 minutes
Range: 30 feet
Components: V, S
Duration: Instantaneous
You summon a spirit that assumes the form of an unusually intelligent, strong, and loyal steed, creating a long-lasting bond with it. Appearing in an unoccupied space within range, the steed takes on a form that you choose, such as a warhorse, a pony, a camel, an elk, or a mastiff. (Your DM might allow other animals to be summoned as steeds.) The steed has the statistics of the chosen form, except that it has a +1 bonus to its Strength, Constitution and Dexterity scores above that of normal creatures of the chosen form. While it appears normal, it is actually a celestial, fey, or fiend (your choice) instead of its normal type. Additionally, if your steed has an Intelligence of 5 or less, its Intelligence becomes 6, and it gains the ability to understand one language of your choice that you speak.
Your steed serves you as a mount, both in combat and out, and you have an instinctive bond with it that allows you to fight as a seamless unit. While mounted on your steed, you can make any beneficial spell that targets you also target your steed.
When the steed drops to 0 hit points, it disappears, leaving behind no physical form. Anything equipped on the steed (tack, harness, barding, saddle bags, etc.) disappears along with it. Casting this spell again summons the same steed, restored to its hit point maximum and with all equipment intact.
You can also dismiss your steed at any time as an action, causing it to disappear into a pocket dimension where it awaits your summons. Anything equipped on the steed (tack, harness, barding, saddle bags, etc.) disappears along with it. As an action while it is temporarily dismissed, you can cause it to reappear in any unoccupied space within 30 feet of you.
While your steed is within 1 mile of you, you can communicate with it telepathically.
While mounted, the rider can choose to either control the steed or allow it to act independently (see PHB 198).
The mount is extremely loyal and always has the best interests of its bonded rider in mind. It will never intentionally act in a way that would be to its master’s detriment or against its master’s wishes.
You can’t have more than one steed bonded by this spell at a time. If you cast this spell while you already have a bonded steed, you instead cause it to adopt a new form. Anything equipped on the steed at the time (tack, harness, barding, saddle, etc.) transforms to fit the steed’s new form as well.
Level 7
Mounted Charge
At 7th level, your training allows you to make a special attack while mounted. As an action when mounted, you can have your mount move up to its base speed, but a minimum of at least 15 feet in a straight line and then you can make a single attack with a melee weapon. For this attack, your normal proficiency bonus is doubled. On a hit, you deal extra damage equal to three times your proficiency bonus.
Level 10
Improved Bonded Steed
You now have further choices as to the form of your chosen steed. Beginning at 10th level, in addition to the previous forms mentioned in the Summon Steed spell, you can also choose to have your steed take the form of a flying or underwater creature. The steed takes on a form that you choose, such as a pegasus, giant eagle, hippogriff, griffon, giant sea horse, or hunter shark. (Your DM might allow other animals to be summoned as steeds.)
Level 15
Improved Mounted Charge
Your mount now charges through enemies trampling them beneath it. Starting at 15th level, as an Action Surge, you can have your mount charge through occupied enemy squares as long as the enemy creature is of a size category smaller than your mount. The mount must move in a straight line for at least 15 feet before moving into the first enemy space. It can continue to move forward in a straight line up to its total normal movement and trample up to 2 additional enemies. The creature must make a Strength saving throw (DC 8+Proficiency+Mount's Strength Bonus) or fall prone and be trampled for the normal amount of damage done by the mount's type or as is decided by the DM. For example, the hooves of a warhorse do 2d6+4 bludgeoning damage. So, at most, the mount could trample 3 enemy creatures by moving in a straight line for at least 30 feet.
Level 18
Inspiring Charge
The sight of you charging into battle serves as a source of inspiration for your allies and dread for your foes. Starting at 18th level, when you perform a mounted charge you may also chose to use a bonus action and upgrade it to an inspiring charge.
For one minute you and all allies that begin their turn within a 30 foot radius of your position receive advantage to their attack
rolls. Likewise, all enemies that begin their turn within a 30 foot radius of your position receive disadvantage to their attack
rolls. Once you use this feature, you can’t use it again until you finish a long rest.
Thoughts?
Level 3
Beginning when you choose this archetype at level 3, you gain two attributes. First, whenever you’re mounted you gain a +2 bonus to your Armor Class as well as a +2 bonus to your Initiative.
Second, you gain the ability to cast the spell “Summon Steed” once per long rest.
Summon Steed (Based on the spells “Find Steed” and “Find Familiar”)
Casting Time: 10 minutes
Range: 30 feet
Components: V, S
Duration: Instantaneous
You summon a spirit that assumes the form of an unusually intelligent, strong, and loyal steed, creating a long-lasting bond with it. Appearing in an unoccupied space within range, the steed takes on a form that you choose, such as a warhorse, a pony, a camel, an elk, or a mastiff. (Your DM might allow other animals to be summoned as steeds.) The steed has the statistics of the chosen form, except that it has a +1 bonus to its Strength, Constitution and Dexterity scores above that of normal creatures of the chosen form. While it appears normal, it is actually a celestial, fey, or fiend (your choice) instead of its normal type. Additionally, if your steed has an Intelligence of 5 or less, its Intelligence becomes 6, and it gains the ability to understand one language of your choice that you speak.
Your steed serves you as a mount, both in combat and out, and you have an instinctive bond with it that allows you to fight as a seamless unit. While mounted on your steed, you can make any beneficial spell that targets you also target your steed.
When the steed drops to 0 hit points, it disappears, leaving behind no physical form. Anything equipped on the steed (tack, harness, barding, saddle bags, etc.) disappears along with it. Casting this spell again summons the same steed, restored to its hit point maximum and with all equipment intact.
You can also dismiss your steed at any time as an action, causing it to disappear into a pocket dimension where it awaits your summons. Anything equipped on the steed (tack, harness, barding, saddle bags, etc.) disappears along with it. As an action while it is temporarily dismissed, you can cause it to reappear in any unoccupied space within 30 feet of you.
While your steed is within 1 mile of you, you can communicate with it telepathically.
While mounted, the rider can choose to either control the steed or allow it to act independently (see PHB 198).
The mount is extremely loyal and always has the best interests of its bonded rider in mind. It will never intentionally act in a way that would be to its master’s detriment or against its master’s wishes.
You can’t have more than one steed bonded by this spell at a time. If you cast this spell while you already have a bonded steed, you instead cause it to adopt a new form. Anything equipped on the steed at the time (tack, harness, barding, saddle, etc.) transforms to fit the steed’s new form as well.
Level 7
Mounted Charge
At 7th level, your training allows you to make a special attack while mounted. As an action when mounted, you can have your mount move up to its base speed, but a minimum of at least 15 feet in a straight line and then you can make a single attack with a melee weapon. For this attack, your normal proficiency bonus is doubled. On a hit, you deal extra damage equal to three times your proficiency bonus.
Level 10
Improved Bonded Steed
You now have further choices as to the form of your chosen steed. Beginning at 10th level, in addition to the previous forms mentioned in the Summon Steed spell, you can also choose to have your steed take the form of a flying or underwater creature. The steed takes on a form that you choose, such as a pegasus, giant eagle, hippogriff, griffon, giant sea horse, or hunter shark. (Your DM might allow other animals to be summoned as steeds.)
Level 15
Improved Mounted Charge
Your mount now charges through enemies trampling them beneath it. Starting at 15th level, as an Action Surge, you can have your mount charge through occupied enemy squares as long as the enemy creature is of a size category smaller than your mount. The mount must move in a straight line for at least 15 feet before moving into the first enemy space. It can continue to move forward in a straight line up to its total normal movement and trample up to 2 additional enemies. The creature must make a Strength saving throw (DC 8+Proficiency+Mount's Strength Bonus) or fall prone and be trampled for the normal amount of damage done by the mount's type or as is decided by the DM. For example, the hooves of a warhorse do 2d6+4 bludgeoning damage. So, at most, the mount could trample 3 enemy creatures by moving in a straight line for at least 30 feet.
Level 18
Inspiring Charge
The sight of you charging into battle serves as a source of inspiration for your allies and dread for your foes. Starting at 18th level, when you perform a mounted charge you may also chose to use a bonus action and upgrade it to an inspiring charge.
For one minute you and all allies that begin their turn within a 30 foot radius of your position receive advantage to their attack
rolls. Likewise, all enemies that begin their turn within a 30 foot radius of your position receive disadvantage to their attack
rolls. Once you use this feature, you can’t use it again until you finish a long rest.
Thoughts?
