Dark Cathedral and Necromancer and new item: cloaking device

During a thunderstorm, in a random location, a huge dark cathedral will appear, lasting for 1 Minecraft day after the storm. This huge, imposing cathedral will be home to Minecraft's newest mob boss- the Necromancer and another type of lesser mob- Shadows. Shadows are black ghost/spectre- like mobs who float around, wailing and only attack or are attackable once you enter the cathedral. Their attack consists of a shadow dart that deals the same damage as a skeleton arrow but initiates no knockback. They have ok HP. Necromancers are powerful dark figures, who summon ghosts when attacked and also shoot black darts from their staffs that do high damage. They have superior HP to players. When killed, they drop a cloaking shield, which isn't a stackable item and has durability like a diamond sword. (more on this later). Necromancers also drop shadow particles which repair cloaking shields and netherite ingots. Cloaking shields, when activated, allow the player to become invisible to all mobs/ other players and reduce attacks received for 5 minutes before needing recharging. It takes 5 days to recharge in a charging block- made from 5 shadow particles and a netherite ingot. Loot in the cathedral includes shadow particles, horse armour, diamonds, netherite, saddles and golden apples, iron and occasionally diamond armour. If a player remains in cathedral as it is disappearing they will be teleported to their bed.