Royal Guard

Royal Guard (ロイヤル・ガード) is a military branch of the Imperial Army specially chosen to protect the Imperial Palace.

Background
The Royal Guard are elite knights under the direct command of the Emperor. They are elites among the elites in the Empire.

The Invaders of the Large Tomb Arc
When a dragon appeared on the palace grounds of the Imperial Capital, forty Royal Guards surrounded it. Two dark elves that flew in riding a dragon, demanded to see the emperor lest there be consequences. To make their point, one of the dark elves created a massive crater that swallowed the defending knights and royal guards.

The Magic Caster of Destroy Arc
Several Royal Guards accompanied Emperor Jircniv on his entourage to the Great Tomb of Nazarick where a meeting with Ainz Ooal Gown is conducted thereafter.

Strength
The Royal Guard are equivalent to Gold-class adventurers. The Royal Guard's knights are equipped with full plate armor imbued with magic, holding magic shields and magic weapons forged and enchanted by the many magic casters of the Empire, a fortune that was worth more than their weight in gold.

Trivia

 * Forty Royal Guards were killed during Mare and Aura's visit to the Imperial Palace.
 * In the Anime, the Royal Earth Guard and the Royal Guard wear the same equipment and armor.