One of the core ideas I use in my games is one I learned long ago from Champions and from an excellent 2e encounter is this
Game Balance is in the Numbers not in the flavor. In D&D terms this means a spell is 3rd level not because its a Fireball but because it does 1d6 per level in a 20 radius. Push comes to shove, it doesn't matter if the spell is fire, ice, screaming skulls and puss yellow beetles so long as the level is the same and the relative ability to defend remains.
Now later editions can complicate things with spell schools and such (certain specialties do not get certain kids of magic effects) but as a general thing you can name a monster, a spell or a class whatever you want and "reskin" it as anything and it won't hurt your game.
In my next post, you'll see how this can be applied to allow D&D, especially the later editions to make almost any kind of character ...
The Return of Planescape? - Curious. There is a brief note on this 'countdown' at Enworld.
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