Portal Rocks, by Jeffrey D. Clark

A boy's bedroom.  It's under control messy.  The boy--fifth grade, but still on the young side--sets up scenarios with his toys, then leaves them set up with the intention of coming back.  He keeps moving on to play with something else, so at the end of the day, you can see everything he's been up to.  Walking through the room is sort of like trying to play a real life version of "Operation" where the slightest misstep is going to set off an alarm.  He's clearly a collector--his mom says packrat--and there are categorized piles of trinkets, pieces of things, and shiny objects all about.

So that is why today's game--Castle Battle--must take place outside.  With no viable real estate left in the bedroom, the decision is quickly made to lug, it seems, most of the remaining contents of the room outside to set up elaborate castles, which the boy and the neighbor kid will then attempt to destroy.  It's a colossal battle scenario.

Taking turns, they fling objects at each other's fortresses, making up new rules with almost every turn.  Quite a spectacle.  Especially since the boys have found that the loose, dry dirt makes pretty cool explosion effects.

The original game abandoned, now the objective is to make the biggest dirt explosion.

After a particularly good one, the boys notice a bright, blue, glowing rock has been exposed.  Being boys of the collector mindset, it is quickly unearthed and promptly fought over.  In the scuffle, more rocks like it are found.

These are now deemed magic ammunition and can be thrown at the opponent's castle if you use a wizard knight.  So it is done.   And the wizard knight becomes the hardest working piece for both sides

It is soon noticed that these mysteriously glowing blue rocks of wonder make sparks!  And if you throw two at the same time, you can see little blue lightning connecting the pair.

New rules are added and now, if the wizard knight's ratio of hit points to armor class is high enough, he can cast a spell to bring out the Ogre Mage, which has significantly higher destructive capabilities--in the form of larger spells.

"My wizard knight is gonna call out the Ogre Mage, so since this is the first time he's in, he's really well rested and ready for battle.  So his first attack spell uses all five rocks!"

"Ok.  I'm calling out my secret weapon!"  

And Boy Two introduces the secret weapon:  a new defender in the form of a shiny green beetle, unaware that it has been drafted into the raging conflict.

"Aaagh!  Goblin Scuttler!  Change attack!"  And Boy One jumps back, spinning into a last ditch defensive dive that only a ten year old boy can properly execute.  Just before he hits the ground, he flicks his wrist and hurls all five rocks at the rapidly approaching new enemy of destruction.

Both boys watch in surprise as the rocks begin to sizzle and hum.  They form into a spinning pattern with lightning spokes.

As they hit the ground, there is a pulse, and a flash, and, as the boys describe later, a noise like sound backwards.  And the goblin scuttler--the beetle--is gone...

So are the rocks.

The two boys stare at the ground where the beetle had been.  Then they look at each other.  And back at the ground.

"What happened?"

"I dunno."

"Where did they go?"

"I dunno."

They sit in stunned silence, just staring.  Then the moms call that it's time for dinner and besides that, it looks like rain.  So the boys head inside.   

It hasn't rained for weeks.  The heat is intense.  And thunderclouds are moving in...

With the first roll of distant thunder, the ground actually begins to pulse with a dull glow.  Not so you would really notice, because it's not dark enough yet.  But surrounding all of the homes and yards of the small neighborhood where the boys live, are patterns of intersecting circles on the ground.

Intersecting circles made from the same rocks that had just disappeared in front of the boys...

As the thunder gets closer and the drizzle turns to serious rain, the patterns glow brighter and the pulsing becomes a constant hum...

In the morning, after a spectacular lightning storm, the regional news and the authorities have a question...

Where are all the residents of Cutlerville?