The level of your construction research determines which magic items you are allowed to craft. Some construction spells also allow you to make magic units. - Illwinter.

Construction mostly allows you to forge items; every even-numbered level in Construction opens up a new tier of items for you to forge.

Odd numbered levels in Construction offer a few new spells. The most significant of them are Legions of Steel (enhancing troops' armor) and Weapons of Sharpness (allowing your troops to cut through armor).

• Fire
• Air
• Water
• Earth Create mechanical warriors. also Great for buffing troops with Leigons of Steel, and Weapons of Sharpness.
• Astral
• Death
• Nature

• Fire & Earth super Late game create Iron Dragon for fun.
• Death & Air can make Corpse Man Constrution which are great in terms of gems to chaff numbers if you have the associated gear.
• Death & earth super Late game create Poison Golem for fun.
• earth & astral make the great Super comabten chassi with Golem Construction.
• nature & death Create Undead plants with high fatigue vine attacks.