The Clock Tower

The Clock Tower was a massive and ominous bell tower, standing tall in the center of the Tannhauser capital Bosch. With grand features, such as smaller spires, windows and an intricate design, this tower was reported to have fallen from the sky, crushing the capital and laying to near complete ruin. Accompanied by a host of angels laying waste to the rest of the country, the tower was the center of conflict in the Three Tannhauser arcs. 
It was made of the same chaos energy that created Castle Crowhenge, and just as with that place, it came from above, drawing its power from this higher realm. Its arrival was heralded by the Prince of Tannhauser, with him summoning it in order to act out his plan of bringing The Heavens down to the mortal realm and bring the Angels down as well. 
The tower itself had some interesting properties. Being the center of the invasion, a new wave of these angel-like monsters arrived with every strike of the bell within the tower, an occurrence which appeared to be entirely random, although approaching the tower did seem to trigger it. Closer to the tower, a different Angel was spooted, writing the word 'Oathbreaker' across the ruins of Bosch. However, it drew its power separately from the tower and was even opposed to it, as seen by its conflict with another Angel that emerged from the tower, the massive centipede-like Goliath. Also of note, was the fact that some residents of Tannhauser report it to have always been there, as if not remembering it falling out of the sky, possibly due to the effects of the tower slowly transforming the populous into merely an extension of its power. 
The tower itself had a glassy and sandy texture, almost like chalk. Its features became less distinct closer up, as if designed to be viewed from a distance, and the ground directly surrounding the tower can be seen coated with the sand-like substance that makes out the tower. The tower itself was made of Celestial Silver, and when any of the Angels protecting it fall, the Celestial Silver they were composed of would melt into the ground to reinforce the tower. Much like these Angels, as seen through Gregor's Pandimensional Sight, it was impure, however, the tower was surrounded by a husk of sand-like Celestial Silver, with each fragment of sand itself being impure however with no shared weakness as a collective. The rooms of the castle that remained intact after the Tower's fall onto it had buckled somewhat under the weight and were generally heavily damaged, with Mercedes observing that the castle grounds seemed to slowly be transforming, blending into itself, much like the lands of The Heavens.
While the surface level of the Tower seemed to mostly be comprised of the old rooms from the Tannhauser Castle, with some alterations due to the rampant chaos magic, the inner workings of the castle appeared very differently. They took the forms of sandy tunnels, with the various Infantry Angels that guard the tower in swarms being formed here, growing out from the walls in clusters. Supporting pillars could be seen throughout these tunnels keeping the ceilings up. With the walls being sand-like in nature, it was possible to traverse through them by submerging oneself in the sand and traveling through to another side. In one of the rooms in the inner levels of the castle was an empty sarcophagus and a discarded royal bell, alongside a pile of some acrid black substance at the end of a corridor, which lead to a wall of forming Angels. There were also some spare replacement bells somewhere. 
Within these walls, the Tower continued to 'digest' the land that once took up the space the tower resided on, using chaos magic to distort it as it became one with the tower, an energy much like that of Castle Crowhenge, and much like when Markus warped through the portal that brought him to Tannhauser from the castle. Notably, in this chaos space, where one thing blends into another, the memories of the location and all things that were once there were accessible, seen through Markus conjuring up party tents of an area he remembered. He was also able to possibly conjure an image of clown Thog using his own memories, but since that never actually existed there it would have taken up considerable energy.
The center of the tower was guarded by a singular entry through an arena-like room surrounding the central support beam for the tower. Past this room was a massive marble-like staircase, formed by the tower to imitate a replica of civilization, leading higher up into the tower that seems to resemble the old castle more. In this place lied a hallway, with a facade of marbles stretching from floor to ceiling, with reflective substances in between them, in which, The Prince of Tannhauser was seen by Markus, refracted through the light of the reflection, though the prince could not see him in turn. The two could hear each other however, before Markus was transported back to his party. When the group returned, the prince was absent, replaced by two cannon wielding horse Angels. Notably, their cannon fire while in this room behaves irregularly, much like Harlock's new arm, bouncing around irregularly. When a projectile was thrown through the mirror, it bounced around within it for a moment, before coming out of the other side. With these specific dualities, Harlock was also able to predict the behavior of these cannonballs.
As the tower rose up, its architecture twisted and contorted further and further, with pure twisted dark roofs, and structures that 'make less sense'. Its architecture stretched beyond what even a human mind can comprehend. It was described as brutal to look at, causing damage against the eyes and brain. Even further up, the tower became more sandy in texture, with the pillars and walls decomposing further into madness. Numerous mostly composed Angels were found here. It extended higher and higher, until it reached a sandy desert, with a lone throne, for The Prince of Tannhauser. Following his defeat, with no greater entity to maintain its shape, the tower began to collapse. Finally, with the detonation of the explosives the team of Nine Shrines had laid throughout the tower, the tower erupted and collapsed, finally bringing an end to the reign of the Angels. The land surrounding it would become a desert of white sand that will remain for decades.