Reverse Arrancar & Blackout Citadel

Reverse Arrancar are shinigami, who had the separation between hollow and shinigami removed, creating an arrancar level of strength. This can be what a few characters in the original bleach series can be called this, such as kaname tousen. Though they're called Reverse Arrancar, they more resemble a Vasto Lorde in appearance.

Blackout Citadel, is a base of operations for the reverse arrancar and their leader, Yawarakai Kinmekki [柔らかい金メッキ] (Soft knight/ Soft gold plating). The leader's name referring to her being a soft/weak 'knight' of seireitei as her resolve and heart was not in it. And plated gold, well, is reference to her appearing nice and warm, but behind that is dense blackened murderous intent. Which is reflected in the citadel's architecture. It looks like a warmly-lit and feeling location, but inside reveals it's only lit by the windows and inside is very few light sources.