Here is my attempt to convert an Eberron classic prestige class into the 5th Edition. I hope you like it.

The Bone Knight

OATH OF THE BONE
Bone knights are Karrn patriots, living protectors who fight alongside the undead legions of their land. During the Last War, they provided tactical expertise and fine control to the legions of undead Kaius raised to defend his people. In postwar Karrnath, they serve as elite knights who travel abroad to complete missions that serve the greater glory of their king. They wear suits of bonecrafted armor that they create themselves and learn to harness the power of necromancy, turning hordes of undead into disciplined, even cunning, troops.

The Art of Bonecrafting
Paladins of this Oath gather the bones of their fallen comrades and attach them to their armor and weapons for two reasons: to honor the fallen and to bring fear to their enemies. The prosses requires specific skill, both mandane and necromatic, taught only by the knights themselves.

The Knight must gather a specific amount of bones, which he can then forge onto his armor and weapons. This process can be used on any physical weapon or armor and takes 8 hours of effort, or can be incorporated into the forging of new weapons or armor without any significant delay in the construction process. The resulting equipment has a particularly menacing visage, and those that use them in combat sow fear in their enemies. A Bone Knight leading a battalion of Karrnathi undead is a sight that haunts the dreams of any warrior.

You gain proficiency to Intimidation while wearing armor or wielding weapons treated with Bonecrafting. If you are already proficient, your proficiency bonus for it is doubled instead.

When using Divine Smite with a weapon treated with Bonecrafting, the extra damage of the Divine Smite is necrotic instead of radiant.

Oath Spells
You gain oath spells at the paladin levels listed.
 Oath of the Bone Spells
 Paladin Level                      Spells
       3rd                     False Life, Inflict wounds
       5th                     Ray of Enfeeblement , Summon Skeletal Steed
       9th                     Animate Dead , Vampiric Touch
      13th                    Animate Karrnathi Dead, Death Ward
      17th                    Raise Dead , Antilife Shell

Channel Divinity
When you take this oath at 3rd level, you gain the following two Channel Divinity options.

Bone March.You can use your Channel Divinity to rally undead to your command. As an action, choose one zombie or skeleton within 30 feet of you that you can see. The creature must succeed on a Wisdom saving throw or be Charmed by you for 24 hours. While Charmed, the creature must obey your commands to the best of its abilities. Using Bone March on a creature already affected by it refreshes its duration to the full 24 hours without requiring a new saving throw. Additionaly you can use this Channel Divinity on undead created with Animate Dead to expand the duration of your control without casting the Spell again. Creatures whose Challenge Rating is equal or greater than your Paladin level are immune to this effect.

Arms of the Grave.You can use your Channel Divinity to imbue your bonecrafted armor or weapon with necrotic energy. As a bonus action, you choose one bonecrafted weapon you are wielding or one suit of bonecrafter armor you are wearing. If you select a weapon, it deals an extra 1d4 necrotic damage to any target it hits, for one minute. If you select a suit of armor, bludgeoning, piercing, and slashing damage you receive from non-magical weapons while wearing that suit of armor is reduced by an amount equal to half of your Charisma modifier (rounded up, minimum 1), for one minute.

Master of the White Banner
At 7th level, all undead under your control have advantage on saving throws against being turned, and those within 10 feet of you gain a bonus to melee weapon damage rolls equal to your Charisma modifier (minimum 1).

Exoskeleton of Undeath
At 15th level, you learn how to expand the necromantic energies that dwell within bonecrafted armor to affect yourself. You can take one hour to perform a ritual that allows you to fuse a suit of bonecrafted armor on your body. This fused suit cannot be removed except by your death or the same ritual, but otherwise retains its traits. While fused with bonecrafted armor, you gain immunity the poisoned condition and resistance to poison and necrotic damage. Additionally you do not need to eat or drink.

Aspect of Death
At 20th level, you can assume the mantle of death and become a veritable Reaper on the Material Plane. Using your action, you slip away from the grasp of life to enter death's embrace. For 1 minute, you gain the following benefits:

Death Strike. When you roll a 1 or 2 on a damage die for an attack you make with a Bonecraft Weapon, you can reroll that die and must use the new roll, even if the new roll is a 1 or a 2.

Lord of the Dead. Undead creatures under your command are immune to effects that turn undead. Each undead creature that you can see within 60 feet of you at the beginning of your turn is subjected to the effects of Bone March.

 Death Denial. If damage reduces you to 0 hit points, you must make a Constitution saving throw with a DC equal to the damage taken. On a success, you drop to 1 hit point instead.

In order to read the full class details click the link at the begging of the post.

This is interesting. I have been playing a Death Knight in 3.5 rule set for some time now, by way of constructing it via the 3.5 MM rules. I've been thinking about converting it to 5e. Though its completely different, perhaps I"ll make one of these and play it through an see how it does. Thanks for this.

Very well presented, and I believe easily appropriated to non-Eberron settings if one is willing to rework the lore.

I particularly like how you got three very low-level abilities and combined them into something that feels like it would make a difference, in Aspect of Death.

Will you be doing more Eberron conversions?

Thank you. Any feedback you give will be welcomed :)

Of course more are coming, The Phantom Knight will be published today and after a special request from a friend Primal Scholar from Secrets of Xen'drik is on the way.

I really like this! But minor question about the 15th level ability: does the fused suit still have drawbacks to it? For instance will a bone crafted suit of heavy armor that is fused still impose a sneak penalty, or similar effects?

The ability mentions "retains its traits", so I suspect both beneficial and detrimental effects of the armor remain, whether native (such as the Stealth penalty) or by magical enhancement.

At least that's how it reads.

Hellon VanZoeren , thank you for your comment, i hope you play the class and give us more feedback. About your question Onyx gives the exact answer.

So after some feedback from the internet I added some additional features on the class.

- Exoskeleton of Undeath
At 15th level, you learn how to expand the necromantic energies that dwell within bonecrafted armor to affect yourself. You can take one hour to perform a ritual that allows you to fuse a suit of bonecrafted armor on your body. This fused suit cannot be removed except by your death or the same ritual, but otherwise retains its traits. While fused with bonecrafted armor, you gain immunity the poisoned condition and resistance to poison and necrotic damage. Additionally you do not need to eat or drink.

Hey can you please post the stats for animate Karrnathi dead? Sounds interesting.

I like the bone march. There's some nasty power in it. (free demilich pet for 18th level players). The other abilities are quite weak in comparison though.

Check the link if you want to see the full class option including karrnathi undead as well as the spells.

Have in mind that in this edition numbers matter. Karrnathi undead are designed as 1 challenge rating. Having 2 or 4 around you (and dealing your CHA modifier damage) at any level is considered a great boost.  Having 2 of those undead can give you an average extra 20 damage per round.

Also bone march works only on zombies and skeletons.

20 extra average damage and meat (or bone) shields that last longer than normal, to draw enemy fire.