The known world is surrounded by magical storms of intense fury and power. They come about whenever two or more elemental planes intersect, and the raw magical energy contained in them is sufficient to change the nature of the world around them. As they rage, sections of the storm break off and float into the material plane, investing their magical energy into anything they encounter until they run out of energy and fizzle away. No living things are known to live in or even around these storms, as they would be warped, destroyed, teleported, or any number of other bizarre magical effects. The only inhabitants are the dragons of air, who live and play in these storms, changing form and accompanied only by legions of living spells.
Rogue storms that break off from the big storms/walls separating octants would generally continue going until they find a way to bleed of energy without that storage immediately decaying and returning to the storm.
One thing that can happen is "leveling up" things exposed to the storm, granting new abilities and forms, as a way to force more magic into existing things. This is where cool stuff comes from.
Another occurence is that the storem creates an "echo" of forms already exposed to it's energies, multiplying existing designs to rapidly dump energy, although this would be relatively infrequent, tending to be what finally ends the storm. This is why gems tend to appear in clusters of the same type rather than as many types all jumbled together, and allows unique creatures to exist as swarms with fairly homogeneous traits, for ease of play.
Finally, sometimes the storm creates novel structures, by "reclassing" existing ones (goblin becomes goblinoid fire elementalish thing), or through random chance having something end up stable (storm could be treated as large number of spells going off all at once, with backfires and interactions all over the place). These simple forms would be amplified and echoed to produce gems and living spells, with a crude natural selection for stability, as anything too unstable would have fewer chances to be echoed.
There are of course a nearly infinite range of "storm effects", including a shuffle or merging of traits, strange and random mutations, inexplicable magical effects that do *not* change the fundamental nature of beings, and many other unclassified effects.