Erakhan, being a Dragon God, has the power of that would bring death and destruction to his enemies. But he also has another title, the Shadow Monarch. 

With Y/N being the Black Dragon Emperor, he can extract the shadows of dead monsters or warriors and bring them back to live as his shadowy undead soldiers. 

Abilities: 

While some shadow soldiers have abilities unique to themselves, they all share the same set of basic powers.

Regeneration: Shadow soldiers possess incredible regenerative capabilities and cannot be killed by normal monsters, as they can completely regenerate even if their bodies are torn to shreds. 

Conversation: Shadow soldiers who are at least General Grade are able to talk. However, they are only able to communicate in monster tongue, meaning that most humans can't understand them.

Growth: Shadow soldiers are able to steadily grow in power by killing monsters in battle.

Shadow Infiltration: At the Shadow Monarch's discretion, shadow soldiers are able to hide within the shadows of other humans. While doing so, they are able to watch and observe everything happening around the person that they are anchored to. They are also able to send signals to the Shadow Monarch in case the humans they are planted on are attacked, regardless of how large the distance is between them.

Transformation: A unique feature accessible to a master of the Authority over Death, shadow soldiers can be transformed into a weapon or any item to their master's whims. 

Ranks: 

Shadows are categorized into different grades, which reflect their level of strength and work similarly to how do for hunters. While shadows can level up over time by killing their opponents in battle, they cannot advance to higher grades without authorization from the Shadow Monarch. Shadows extracted from particularly powerful beings can also start at a higher grade immediately after their creation.

Basic Grade : The lowest tier, these shadows are the weakest in the shadow army and can be as strong as E-rank and D-Rank Hunters.

Normal Grade : Shadows of this grade serve as foot soldiers in the shadow army and can be as strong as C-Rank Hunters.

Elite Grade : Shadows of this grade are the most common in the shadow army and are about as strong as B-Rank Hunters.

Knight Grade : Shadows of this grade are about as strong as A-Rank Hunters and can be given names by the Shadow Monarch.

Elite Knight Grade : Shadows of this grade are about as strong as basic S-Rank Hunters such as .

Commander/General Grade : Shadows of this grade are immensely powerful and are strong enough to contend with, and even overpower advanced S-Rank Hunters such as . They are also capable of speech.

Marshal/Commander Grade : This grade is the highest that a shadow can evolve to, making those who reach this level the most powerful soldiers in the shadow army.

Grand Marshal Grade : The ultimate rank, this grade is reserved for the strongest shadow in the entire shadow army. The shadow of this grade also serves as the lieutenant to the Shadow Monarch himself.

High rank and most powerful Shadows: 

Igris (Knight, Rank: Marshal Grade)

Tank (Ice Bear, Rank: Knight Grade)

Iron (Human, Rank: Elite Knight Grade)

Blades (Ice Elf, Rank: Elite Knight Grade) 

Tusk (Orc, Rank: General Grade) 

Cerbie (Cerberus, Rank: Elite Knight Grade)

Bigrock (Stone Golem, Rank: Elite Knight Grade) 

Kaisel (Wyvern, Rank: Knight Grade) 

Kaya (Ant Queen, Rank: General Grade) 

Beru (Ant King, Rank: Generał Grade) 

Jima (Naga, Rank: Elite Knight Grade) 

Kamish (Dragon, Rank: Marshal Grade) 

Greed (Human, Rank: General Grade) 

Bellion (Ruler, Rank: Grand Marshal) 

Gojira (Kaiju, Rank: Marsel Grade) 

Karina (3-Headed Dragon, Rank: General Grade) 

Kronos (Titan, Rank: General Grade) 

Uriel (Archangel, Rank: General Grade) 

That's all for the Shadow Army. I hope you guys like it. 

Next up will be either one of the crossover harem or Y/N's peerage. If you have any ideas, let me know at the comments below. Peace out and enjoy!