Spellcasting and summoning.

The creation of a phantom is influenced by the hero's level; the higher the level, the faster the phantom will make its first move, and upgrading the summoning skill will allow you to summon creatures of levels 5, 6, and 7. Spellpower does not have an effect.

The Wall of Swords depends on spellpower and will have more hit points. And the Hive will deal more damage and attack more frequently with a higher spellpower value.