Fireball Seal

This magical piece of paper is known as a Mageseal. When it is torn or damaged, it triggers a searing hot explosion of fire. It is commonly glued or placed over the crack of a door or chest, so that opening it causes it to tear.

Activation

Trigger. The magic is activated when the seal is torn or damaged, such as when the door or object it is on is moved.
  Effects. All creatures within 20ft. of the seal have to make a Dexterity saving throw (DC 16). On a failed save they take 10d6 Fire damage. On a successful save they take half damage. The fire spreads around corners. It ignites flammable objects in the area that aren’t being worn or carried.  

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Countermeasures

Like most mageseals, a fireball seal can be easily spotted. Removing, bypassing or disabling it is however still quite tricky. The seal is quite obvious unless it is properly hidden by the person who placed it, but knowing what effect might occur requires proper analysis. Use the following phases and ability checks to determine successes or failures.   Disarming Information

Phase	Ability Check
Detection	Perception (DC 10)
Analysis	Investigation (DC 16)
Solution	Sleight of Hand (DC 18)

^{A successful Analysis lowers the Solution DC by 1}   Solution (Sleight of Hand). Read the following text when a character successfully disarms the trap using a Sleight of Hand check.    

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Alternative Solutions

Arcana. Analyzing the trap with a successful Arcana check (DC 16) reveals the effects of the seal. Dispel Magic will not work to remove the magic, but an individual may be able to use a spell such as Mage Hand to break the seal while standing at a safe distance from the effects.