Your strategy for playing as Necropolis.

Archers deal decent damage, but they struggle against demons.

Are you referring to mana drain, which is already scarce? If the opponent is Inferno, maximizing the hero's initiative helps, so they can move before their demons and cast a powerful spell on them. This involves finding artifacts that increase initiative and leveling up spellcasting, along with investing in Sharp Mind through Education/Logistics. However, this doesn't always work.