Here is another installment of exTRAPaganza, our Thursday over-the-top trap series.
A long hallway slopes down. Overhead hang many large globes of light.
When a creature passes under a globe, it falls on the ground and rolls downwards. The globes act as a globe of fire. Each round it moves 10 feet downhill. Any creatures that it passes through or any creatures that pass through it take 2d6 fire damage. If a globe ends it turn on a creature, that creature takes 2d6 fire damage. If a creature starts its turn on a globe, that creature takes 2d6 fire damage.
When all the balls reach the end of the hallway, they all explode. This explosion deals 6d6 fire damage per globe to all creatures within 60 feet. This damages is reduced by half with a successful Dexterity saving throw.