Chamber

Chamber is a level 309 ghost-like creature found in The Broken Halls, and was also The Cohesive's "Crowning achievement". Chamber will spawn after the player has interacted with the Journal orb, although this can only be done once a week. He will not appear if the character is wielding a Zaros weapon

Tactics
Chamber is able to attack with magic and melee, and will alternate between all three main protection prayers when necessary with a three-second pause between each switch (Aka, if the player is attacking with range and switches to melee, it will take three seconds for Chamber to switch to protect from Melee), which can make it extremely difficult to solo him, along with his powerful unique spells and high maximum hit. However, he is weak against fire spells.

Trivia

 * Chamber is the most powerful monster in the broken halls.