Demiplanar Arena (5e Trap)
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A small snowglobe, inside of which is a gladiatorial arena, rests alone in an empty room. A successful DC(20) Perception check can identify the item as a trap.
When a creature begins or ends its turn within 15ft of the globe, it must succeed on a DC(18) Strength saving throw against being sucked into the demiplane locked within the globe. If there are no creatures currently within the globe when a creature enters it, the globe creates two vrocks that engage the creature in combat.
A creature automatically exits the globe if it is reduced to 0 hit points, or when it has reduced all other creatures to 0 hit points using an attack or spell. The vrocks created by the globe vanish into nothing upon defeat.
The demiplane within the globe is a circular Romanesque gladiatorial arena that is 60ft in radius. The stands are filled with blurry visages of spectators who roar and cheer with every bloody kill that the globe takes. The floor is made of sand and the air is very dry. The sky is perpetually day and free of all weather.