Erich String Orchestra

Erich String Orchestra (エーリッヒ擦弦楽団) is a group of musicians that serve under Chacmool in the Great Tomb of Nazarick.

Background
Presumably, these Greater Doppelgängers were created either directly or indirectly by the guild member, Temperance.

The Paladin of the Holy Kingdom Arc
They made their first appearance under the form of Yuri Alpha and Lupusregina Beta. Alongside the summoned Evil Lord Wrath and Aureole Omega, the five Greater Doppelgängers in the form of every Pleiades member except Narberal Gamma were present when fighting against the Sorcerer King, Ainz Ooal Gown.

Strength
So far, the musicians are estimated to be at least over five members strong. They also appear to be Greater Doppelgängers. As doppelgängers, they should have the racial feature of taking on the appearance of different people and using their abilities in the process.

After transforming into almost every member of the Pleiades, they are capable of demonstrating similar powers and teamwork tactics to the original. The group's strength is further boasted when Aureole Omega buffed them. For instance, one of the Doppel-CZ2128 Delta is able to stop Ainz from casting his spell.

Trivia

 * The Orchestra was programmed to refer Temperance as Kurayami no Shirabe.