Druembre is a magic sword described in Monster Girl Encyclopedia World Guide - Side II.
Guide Book Entry
Druembre is a magical sword with a dark power and beauty that can overwhelm a beholder. In the sword's crosspiece shines a dark red light with a magic gem that seems to symbolize Lescatie.
This sword is known as the most powerful of the magical swords in the mamono realm of Lescatie, for it was blessed and filled with the magical power of that country's ruler, Druella. Its power is quite different from other swords made of mamono realm ore: around the blade of Druembre swirls a terrifying stream of mamono mana like that of dark matter, allow the monster to channel this mamono mana. With a single sweep, she can flood the entire space on that side with scarlet mamono mana of Lescatie, which will dramatically accelerate the transformation of the surroundings into a mamono realm. And if the sword has accumulated magical power, it can be dramatically released in a single attack, like a dark warrior's strike, which will deprive the opponent of the magical powers he has. However, the main ability of this special magical sword is that it allows the wielder to look into the opponents' hearts and see their desires in a similar way as Druella herself does.
To the owner of this weapon, when she crosses blade with her opponent's sword, their secret desires will gradually be revealed, information about who her opponent is in love with and secretly desires, as well as everything that they secretly thinks about this person - these hidden desires will become an open book for the owner of the sword. Normally the mamono realm's weapon's monsterization turns an opponent into a "succubus" in most cases, but since this magic sword has the power of Druella, it can turn girls into representatives of different races, just like the Lilim do. However, with the power of this sword it is also possible to look into the heart of your opponent and turn her into the most suitable mamono, so that her romantic path will be pleasant and reliable. In other words, it is not an exaggeration to say that the wielder of this sword can take on the role of a Lilim, a daughter of the Mamono Lord.
In addition, the Seven Princesses of Lescatie, including Wilmarina, received the same power from Druella. Those who have come into possession of this sword often take part in invasion expeditions whose goal is the large-scale monsterization of opponents. During such sorties, they must, along with the Seven Princesses, move in the vanguard, expanding the mamono realm with their sword strokes.
This magical sword is personally awarded by Druella to the best dark knights, usually the one who has had the most success in expanding the mamono realm. This blade is a proof of trust from Lady Druella, as well as a symbol of hope for monsters who wish the world to be filled with love and new, happier monster couples of husbands and their monster wives to emerge. I would say that this magical sword is the most prestigious for the dark knights.[1]