Small earthen bell with a glass inner cup and clapper. When rung the bell makes a sound like a mix of music and rain. Ring the bell then place it on the ground. A gentle force shield dome will appear centered on the bell with a diameter of about 20 feet and about 15 feet tall. Any slow moving object can move through the force shield. I.e. a person leaning on the force shield will slowly fall into the dome in about 10 seconds. Fresh air moves gently but freely through the barrier as will smoke from a fire inside drift out. Consequently any gas type attack to the internal party will succeed normally.
Every fast moving object like an arrow will appear to hit a completely solid shield. Quick objects such as a swung weapon will bounce as if slamming a block of rubber. Obviously there is a significant chance of the attacker being surprised and therefore suffering his own attack. I.e. he rolls a 17 to attack and he has a 16 AC. Any magical energy blast will hit and spread over the surface of the shield much like a blast of water hitting a glass ball. Approximately 30% of the magical energy will splatter randomly off and back towards it's origin. Slower magical attacks such as a rain of acid from above will roll down the sides of the dome just like rain.
Do NOT expose the bell to extreme amounts of magic. There is a very likely possibility that it will damage or destroy the bell!
The Rainbell protects the occupants from rain, wind, lighting, etc. It does not trap heat or reflect heat, but it does turn a strong wind into a slow breeze. Each Rainbell can hold 5d10 charges and each charge lasts no more than 12 hours, i.e. one night (or day). Ringing the bell activates a charge. If the bell is rung when the shield is in place, the shield is sucked back into the bell. If the elapsed time has been less than 6 hours, there is a 50% chance the charge will be useful again. Recharging the bell should be somewhat expensive.