Just some tips on coming up with hero ideas, I will gives some tips and show you how it works
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First, think of a hero model. Next, make out what the hero class could be.
E.G. Footman- Warrior (Simple)
Next, associate the hero type with the kinds of attacks the hero would use.
E.G. Warrior- Slashes, cuts, guards etc.
Think more about what these skills could be. (Name first)
E.G. Slash= Power Slash
Now, think about the name of the spell, what could it do?
E.G. Power Slash-> deals Str*10 in damage and stuns unit.
Change the spell's stats to whatever you think fits, if it is an ultimate, make it stronger.
E.G. Power Slash (Ultimate) -> deals Str*15 +150 damage & stuns
Repeat the steps until you come up with four spells, taking note that the spells should complement each other.
E.G. Power Slash, Red Sword (+dmg for next attack/spell cast), Guard (chance to block attack), Offense & Defense (increase dmg and armour)
You see from above that the hero focuses mostly on attacking and defending. This will be the hero's theme. Based on what the hero's theme is, create whatever spells fit.
Finally, do some touch-up on the hero, balance him, change his stats, change his model etc.
That is the general guide to making the hero in my opinion.
I might write a tutorial about this.
PS: You can use the footman hero thing