Yeah, it was a bit confusing
The original hero design had spellcaster heroes automatically gain spell promotions (like High Magic 2) by upgrading into higher tier versions with those promotions built in.
Then we moved to the promotion-based design, where casters would automatically gain Mage or Archmage type promotions that boosted their strength and acted as promotion pre-requisites, but we still needed a way for the heroes to gain the promotions they would need to cast spells.
Your suggestion as I understand it was one means of doing this.
You suggested having spells requiring the promotions.
So for example suppose we wanted Teclis to gain the High Magic 2 promotion when the education tech was researched and High Magic 3 when Arcane Lore was reached.
Your method (as I understand it) would mean we would need a "Teclis2" spell that required the Eduaction tech, and granted the High Magic 2 promotion. And a "Teclis3" spell that required the Arcane Lore tech, and granted the High Magic 3 promotion.
Since every hero would be getting different spells (Teclis got high magic 2 and 3, ariel got athel loren 2 and 3, etc.), we would have to create 2 new spells for each caster in order to make this work, which seems pretty clunky.
The alternative we are going with is to NOT have casters gain spell promotions for free; they must spend their normal level-up promotions on them.
However, to prevent the heroes from gaining lots of levels early, before they have the tech pre-reqs for the spells, we will prevent them from purchasing non-spell promotions except for Combat 1-5.
So if a caster hero gains enough xp for level 7 (after already gaining combat 1-5), it can't level up any further until you research techs that grant access to more spell upgrades (though it still gains xp) because there are no more promotions to select.
Does that make any more sense?
So a caster hero will ONLY be able to select magic promotions and combat 1-5. They will gain levels rapidly from their Hero promotion, and will spend those promotions buying the spell promotions they need like normal upgrades.
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By "mage spells" and "archmage" spells, I just meant the second and third tier spells that we were going to have the hero casters get for free.
So, "mage spells" would be High Magic 2 for Teclis and "archmage spells" would be high magic 3 in the example above.