They have 5 spells. 3 basic, one ultimate, one super ultimate. Basics and ultimate have 5 levels, super ulti is last level ability.
Super ulti can be a passive. Normal ultimate shouldn't be a passive, though it can if you have a very good idea including the normal ultimate as a passive.
What heroes you should NOT make- a necromancer, fire-connected melee, water mage, somekind of magical archer, vampire, paladin-like one, orc berseker, using Medivh model...
It would be nice if you made a Wind/Sand Mage which would use JetFangInferno's graphics- they are at hiveworkshop.com . Hive is currently down, it will be on again next week. But this hero would require very complex spells.
Here are SURELY free hero templates- ogre, troll(axe and spearthrowing, troll mages, hero), gnoll, bandit, druid, elven swordsman(he has a nice model
)...One more things- heroes should be more or less humanoids, so no wolf, archnatid, chimera heroes. They are gladiators, not beasts, beasts are their enemies
.