Barbarian Hall is a Fighter type Monster Room introduced in Boss Monster: The Next Level
This card has a similar damage output as Neanderthal Cave, and has an almost equally debilitating effect. However, a player could easily play this card without any drawbacks if they use up all their Spells, or have none in their hand to begin with.
Having a Save Point Trap Room built ahead of time, using a Spell card to avoid Barbarian Hall's effect, building Barbarian Hall and then activating Save Point's effect is a way to get around Barbarian Hall's effect to ensure the player still has a Spell card at hand during the turn Barbarian Hall is built.
Barbarian Hall features a new type of monster, the Barbarians, which look somewhat like the Scottish from the movie Braveheart, what with the blue warpaint.
The thing on the plaque hanging above the monsters is a human arm.