I'm reworking the soulless one; now it will attack with a fiery wave, and its health will be more reasonable.
Added 40 seconds ago
There's also a mod that replaces Necromancers with Fallen Angels, Stone Giants, Black Orcs + a few Necromancers, and I have a mod that replaces Demons with Elementals + Dark Gnomes, but they only work together.
Added 3 minutes ago
It's impossible to add new spells to the game or create duplicates. However, there are three spells that might be reworked:
1) Hellfire Wave of the Master (fire element)
2) Diabolic Chain of Biara (air element)
3) Uber Meteor Shower (earth element) - this spell wasn't really used in the game (unlike the first two).
Besides that, there are various prayers, banishments, and battle cries. There are also unit abilities (I wrote about them above) - in short, we need to try to fit these into magical schools or at least tie them to perks.
In one topic on this forum, I saw a mod that adds custom heroes and models for them.
The Elves have a hero there with the "Silvan's Rain" specialization.
The hero has a Meteor Shower spell with damage (40 * hero's magic).
The regular Meteor Shower spell works in the game, so it might be the one you're talking about
