I had this idea for a set of mana generating troops:
Spell: Create x (probably 1-3) colour gems. Then remove all other colour gems and skulls.
eg: Create 2 brown gems and remove all other colours and skulls.
All the same gem type would end up falling to the bottom, giving good mana/ extra turn potential.
If it’s too OP, simply remove the gem creation part of the spell.
It could be a good alternative to trolls, probably giving less mana, but being able to calculate extra turns like gem converters can.
My initial idea was a mythic or legendary troop that did this with skulls. Some kind of barbarian/ warrior type thing.
Spell: Create x skulls and remove all mana gems.
3rd trait: At the start of your turn create x skulls.